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FPIIVHTf  LIBRARY    > 
4  IMOT  COIT. 


AMERICAN  SOCIETY 


OF 


CIVIL  ENGINEERS 


THE  DETERMINATION  OF 

SAFE  YIELD  OF  UNDERGROUND  RESERVOIRS 

OF  THE  CLOSED-BASIN  TYPE. 


RV 


Charles  H.  Lee,  Assoc.  M.  Am.  Soc.  C.  E. 


WITH    DISCUSSION    BY 


Mv.ssRS.    JAMES    OWEN,    G.    E.    P.    SMITH,    O.    E.    MEINZER, 

KENNETH  ALLEN,  ROBERT  E.  HORTON, 

AND  CHARLES  H.  LEE. 


Reprinted  from  Transactions,  Vol.  LXXVIII,  p.  148  (1915). 


1 


253090 


AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS 

INSTITUTED     1852 


TRANSACTIONS 


This  Society   is  not  responsible  for  any  statement  made  or  opinion   expressed 
in  its  publications. 


Paper   No.    13 15 

THE  DETERMINATION  OF 

SAFE  YIELD  OF  UNDERGROUND  RESERVOIRS 

OF  THE  CLOSED-BASIN  TYPE.* 

By  Charles  H.  Lee,  Assoc.  M.  Am.  Soc.  C.  E. 


With  Discussiox  by  Messrs.  James  Owen,  G.  E.  P.   Smith,  O.  E. 
Meinzer,  Kenneth  Allen,  Robert  E.  Horton,  and  Charles  H.  Lee. 


Synopsis  and  Conclusions. 

The  objects  of  this  paper  are  to  show  the  possibility  and  practica- 
bility of  measuring  the  annual  rate  of  recharge  of  underground  reser- 
voirs of  the  closed-basin  type,  and  to  indicate  broadly  the  factors 
which  determine  safe  yield  from  a  basin  by  artificial  development, 
such  as  Artesian  flow  or  pumping. 

The  paper  opens  by  pointing  out  tlie  importance  of  the  problem  in 
California  and  the  Southwest.  Following  this  there  is  a  description  of 
the  physical  features  of  underground  reservoirs  and  the  general  prin- 
ciples of  inflow,  outflow,  and  storage.  The  body  of  the  paper  presents 
detailed  methods  and  results  of  extended  measurements,  by  the  Los 
Angeles  Aqueduct  Bureau  and  the  United  States  Geological  Survey,  for 
the  determination  of  the  rate  of  annual  recharge  of  the  Independence 
Basin,  in  Owens  Valley,  California.  The  subjects  of  percolation  from 
stream  channels,  relation  of  precipitation  and  altitude,  soil  evapora- 
tion combined  with  transpiration  from  grass,  and  ground-water  fluctu- 
ations, were  carefully  studied  in  the  field,  and  original  data  are  pre- 

*  Presented  at  the  meeting  of  May  6th,  1914. 


SAFE    YIELD   OF    UXDEKG  ROUND    RESERVOIRS  149 

sented.     The  paper  closes  with  a  discussion  of  the  relation  which  the 
net  safe  yield  from  a  basin  bears  to  the  rate  of  annual  recharge. 

The  conclusions  are  as  follows : 

1. — The  "underground  reservoirs''  of  California  and  the  South- 
west are  water-tight  rock  basins,  represented  by  the  topographic  valleys, 
which  are  filled  with  porous  alluvial  material  in  which  the  voids  are 
saturated  with  water. 

2. — Inflow  into  these  basins  is  by  percolation  from  water  on  the 
surface  of  the  alluvial  filling,  which  source  may  occur  as  direct  pre- 
cipitation, stream  flow,  irrigation,  or  flooding.  Natural  ground--water 
loss  occurs  in  the  region  of  lowest  depression  of  a  basin,  and  consists 
of  the  breaking  out  of  water  at  the  surface  in  springs  or  seepages, 
evaporation  from  soil,  transpiration,  and  underflow.  Artificial  develop- 
ment, by  wells  or  other  methods,  reduces  the  natural  ground-water  loss. 
Considered  as  averages,  the  rates  of  recharge  and  ground-water  loss 
are  equal,  unless  the  artificial  draft  is  excessive. 

3. — The  rate  of  recharge  in  a  region  of  small  precipitation  and 
high  evaporation  rate  can  be  determined  most  accurately,  and  with 
least  expenditure  of  time  and  money,  by  measuring  the  elements 
which  make  up  the  ground-water  loss.  Of  the  natural  elements,  the 
most  important  are  soil  evaporation  and  transpiration.  The  under- 
flow is  relatively  small  and  often  negligible. 

4. — The  safe  yield  of  artificially  developed  ground-water  obtainable 
from  an  underground  reservoir  is  less  than  indicated  by  the  rate  of 
recharge,  the  quantity  depending  on  the  extent  to  which  soil  evapora- 
tion and  transpiration  can  be  eliminated  from  the  region  of  ground- 
water outlet.  

Introduction, 

There  are  in  California  and  the  arid  States  of  the  Southwest  many 
valleys  underlaid  by  porous  alluvial  material  in  which  the  voids  are 
filled  with  water.  The  ease  with  which  water  can  be  developed  from 
wells  in  these  valleys  and  the  definite  bounds  of  the  water-bearing 
formation  have  led  to  the  use  of  such  terms  as  "underground  lake," 
"underground  basin",  or  "underground  reservoir".  These  terms  are 
in  general  use  among  local  hydraulic  engineers,  and  have  been  adopted 
by  the  California  Courts  in  numerous  recent  decisions  pertaining 
to  the  use  of  diffused  percolating  water  occurring  in  closed  basins. 


150  SAFE   YIELD   OF   UNDERGROUND    RESERVOIRS 

A  problem  which  is  being  presented  to  the  Engineering  Profession 
for  solution  is  the  determination  of  the  safe  yield  of  "underground 
reservoirs",  or  the  net  annual  supply  which  may  be  developed  by 
pumping  and  Artesian  flow  without  persistent  lowering  of  the  ground- 
water plane.  The  answer  to  this  problem  must  soon  be  had  through- 
out the  Southwest,  and  particularly  in  Southern  California,  where  the 
use  of  underground  water  has  advanced  most  rapidly.  The  available 
surface  supplies  of  the  region  are  now  used  so  extensively  that  future 
extension  of  irrigation  must  depend  on  the  underground  supply. 
Already,  however,  the  growing  popularity  of  ground-water  supply  for 
irrigation  and  the  heavy  drafts  made  possible  by  improved  pumping 
machinery  and  cheap  power  are  giving  rise  to  conditions  of  danger- 
ous overdraft  on  many  of  the  so-called  inexhaustible  underground  water 
supplies.  Furthermore,  in  many  of  the  sparsely  settled  valleys  of 
the  Southwest,  where  very  limited  ground-water  supplies  are  available, 
preparations  are  being  made  to  develop  pumped  water  for  irrigation 
far  in  excess  of  the  safe  yield.  The  writer  has  in  mind  such  a 
valley,  where,  out  of  90  000  acres  of  agricultural  land,  filed  on  in  good 
faith  under  the  provisions  of  the  Desert  Land  and  Homestead  Acts, 
it  can  be  said  with  reasonable  certainty  that  not  more  than  2%  can 
ever  be  put  under  cultivation.  In  addition  to  the  use  of  underground 
water  for  irrigation,  it  is  being  developed  extensively  for  municipal 
purposes.  The  City  of  Los  Angeles  derives  its  present  supply  entirely 
from  an  underground  reservoir,  the  San  Fernando  Valley,  and  is 
preparing  to  develop  a  similar  supply  in  Owens  Valley  to  be  held 
as  a  reserve  in  connection  with  the  Los  Angeles  Aqueduct.  A  portion 
of  the  supply  of  both  Oakland  and  San  Francisco  is  developed  from 
underground  sources,  and  the  possibility  of  increasing  largely  the 
ground-water  supply  derived  from  Livermore  Valley  for  the  latter  city 
has  been  the  subject  of  considerable  debate  among  prominent  members 
of  the  Society.  The  problem,  therefore,  i.s  an  important  one.  and  on 
it  depends,  not  only  the  safe  investment  of  capital,  but  also  the  very 
life  of  large  industries  and  communities. 

The  sources  of  underground  water  are  so  difficult  of  measurement 
and  its  movements  are  so  hidden  from  view,  that  the  solution  of  the 
problem,  until  very  recently,  has  been  merely  a  subject  for  speculation 
and  theorj-.  Within  the  past  few  years,  however,  the  study  of  under- 
ground  water   supply   has   been   given   considerable    attention   by   the 


SAFE   YIELD   OF   UNDEKGROUND   RESERVOIRS  151 

United  States  Geological  Survey  as  well  as  by  engineers  who  have 
had  these  problems  to  meet.  Although  the  fact  of  the  existence  of 
these  "underground  reservoirs"  has  been  established,  their  sources 
of  supply  and  outlets  recognized,  and  many  data  regarding  well  fluc- 
tuations have  been  accumulated,  yet  very  little  has  been  done  toward 
developing  methods  of  measuring  the  rate  of  recharge  or  studying 
the  factors  which  limit  the  quantity  of  water  which  can  be  safely 
developed  from  underground  reservoirs. 

The  writer  has  had  opportunity  to  investigate  a  number  of  the 
important  underground  reservoirs  of  California,  and  in  this  paper 
he  presents  certain  general  principles  which  seem  to  him  to  be  justified 
by  the  existing  data.  Although  these  principles  may  seem  to  be  self- 
evident,  yet  the  writer  has  no  knowledge  that  they  have  ever  been 
applied  to  the  practical  solution  of  the  problem  in  hand.  To  show 
the  possibilities  of  tlieir  application,  therefore,  he  presents  data  and 
studies  for  an  underground  reservoir  in  Owens  Valley,  California,  where 
it  was  desired  to  ascertain  the  quantity  of  ground-water  that  could  be 
developed  safely  without  overdraft.  Much  of  this  information  has 
already  appeared  in  print*  in  greater  detail,  but  the  writer  believes 
that  the  subject  is  of  sufficient  importance,  and  the  component  studies 
are  of  wide  enough  technical  interest  to  be  presented  to  the  members 
of  the  Society  for  discussion  and  expression  of  opinion. 

General  Principles. 

The  typical  underground  reservoir  is,  geologically,  a  structural 
basin  filled  with  alluvial  debris  from  the  adjoining  mountain  ranges. 
These  basins  are  the  product  of  faulting  accompanied  by  the  uptilting 
of  a  crustal  block  from  one  side  of  the  line  of  fracture.  The  formation 
is  very  common  throughout  the  Southwest,  reaching  its  most  perfect 
development  in  the  Great  Basin  region  of  Utah  and  Nevada,  where 
the  name  "Basin-Eange"  has  been  applied  to  it.  In  California  the 
basins  are  found  in  the  valleys  of  the  Coast  Kange  and  along  the 
base  of  the  Sierra  Nevada,  Sierra  Madre,  San  Bernardino,  and  San 
Jacinto  Ranges.  The  rock  enclosing  these  basins  is  in  most  cases 
impervious  to  water  and  practically  insoluble.  Along  the  coast  of 
California,  shales  and  cemented  gravels  predominate,  and  are  prac- 
tically non-water-bearing  in  comparison  with  the  porous  gravels 
*  Water  Supply  Paper  No.  294,  U.  S.  Geological  Survey,  1912. 


152  SAFE    YIELD   OF    UNDERGROUND   RESERVOIRS 

filling  the  basins;  and,  in  the  interior  of  the  State,  the  enclosing 
rock  formation  is  largely  granite.  Most  of  the  basins  can  be  con- 
sidered as  closed  except  for  a  subterranean  outlet  usually  known 
as  the  "Narrows''.  This  occurs  at  the  lowest  point  in  the  rock  rim, 
where  the  gravels  contract  into  a  neck  filling  a  narrow  depression 
or  canyon  cut  into  the  confining  rock.  The  quantity  of  underground 
water  escaping  through  such  an  outlet  is  usually  very  small,  however, 
as  has  been  shown  by  a  number  of  well-known  underflow  observations. 
Hence,  the  underground  reservoirs  can  generally  be  considered  as 
closed  rock  basins,  the  effective  storage  capacity  of  which  is  the  void 
spaces  between  the  particles  of  sand  and  gravel  with  which  they  are 
filled. 

The  usual  sources  of  supply  for  vmderground  reservoirs  are  perco- 
lation from  flowing  surface 'Streams,  from  precipitation,  or,  where  the 
supply  is  not  ground-water  derived  from  the  basin,  from  irrigation 
on  the  surface  of  the  porous  gravels.  The  water  thus  absorbed  sinks 
downward  to  the  general  ground-water  plane  and  then  moves  later- 
ally toward  the  region  of  lowest  depression.  This  region,  in  contrast 
to  the  surrounding  dry  soil  or  desert,  is  usually  characterized  by 
springy,  swampy  conditions,  and  is  commonly  known  in  Southern 
California  as  a  cienaga.  The  natural  outlets  for  underground  water 
are  by  springs  or  seepages  discharging  into  the  surface  channels  which 
drain  the  cienaga,  by  evaporation  from  damp  soils  and  vegetation 
within  the  cienaga,  and,  to  a  limited  extent,  by  underflow  from  the 
basin.  The  surface  streams  formed  by  the  oozing  out  of  underground 
water  join  to  form  a  larger  stream,  which  in  all  respects  corresponds 
to  the  outlet  of  a  lake  or  reservoir,  and,  passing  from  the  basin,  pur- 
sues its  course  just  as  any  other  surface  stream.  Its  flow  is  character- 
ized by  permanence  and  regularity,  except  as  it  is  augmented  by 
surplus  flood  water  which,  during  a  limited  period  following  winter 
storms,  passes  from  the  basin  without  being  absorbed  by  the  gravels. 

The  general  principles  of  inflow  into  and  outflow  from  an  under- 
ground reservoir  of  the  type  described  correspond  with  those  of  sur- 
face reservoirs.  The  difference  lies  in  the  relative  speeds  with  which 
the  general  water  surface  assumes  a  horizontal  position  following  in- 
crease or  decrease  of  volume  stored.  In  the  case  of  a  surface  reservoir 
or  lake,  the  effect  of  inflow  or  outflow  is  an  immediate  complete  re- 
adjustment of  surface  level.     The  frictional  resistance  offered  by  the 


SAFE   YIELD   OF   UNDERGROUND    RESERVOIRS  153 

particles  filling  an  underground  reservoir  is  so  great,  however,  that 
the  movement  of  water  from  an  area  of  high  level  is  verj'  slow,  varying 
from  a  few  hundred  feet  to  a  few  feet  per  day,  depending  on  local 
conditions.  As  a  result,  the  water  surface  in  an  underground  reser- 
voir is  never  horizontal,  being  steepest  near  the  mouths  of  the  moun- 
tain canyons,  the  run-off  from  which  is  the  most  important  source 
of  supply;  it  is  most  nearly  horizontal  at  the  region  of  outlet;  and 
varies  in  slope  and  elevation  from  time  to  time,  depending  on  the 
rate  of  recharge. 

The  average  rates  of  inflow  and  outflow  of  an  underground  reser- 
voir must  be  equal,  otherwise  there  would  be  persistent  rise  or  fall 
of  ground-water  levels  until  such  a  balance  is  reached.  There  are, 
therefore,  two  possible  methods  of  measuring  the  rate  of  recharge, 
either  by  determining  the  total  percolation  from  various  sources  into 
the  porous  material  of  the  basin,  or  by  determining  the  ground-water 
losses.  The  first  method  is  to  be  preferred  where  the  source  of  per- 
colation is  almost  entirely  stream  flow  from  which  channel  losses  can 
be  accurately  measured;  or  where  the  precipitation  is  large,  well  dis- 
tributed through  the  year,  and  forms  the  principal  source  of  supply. 
The  first  of  these  conditions  could  occur  only  in  an  arid  region, 
and  the  second  is  typical  of  humid  regions. 

The  method  by  determination  of  ground-water  losses  is  one  pecu- 
liarly adapted  to  arid  or  semi-arid  conditions  with  high  evaporation 
rate,  such  as  exist  throughout  the  Southwest.  It  has  been  the  writer's 
observation  in  this  region  that  soil  evaporation  and  transpiration 
constitute  from  50  to  100%  of  the  ground-water  losses  from  under- 
ground reservoirs,  the  average  exceeding  75  per  cent.  Other  losses 
are  largely  the  flow  from  springs  and  seepages,  which  can  be  measured 
with  precision.  Eates  of  soil  evaporation  and  transpiration  from  grasses 
do  not  present  insurmountable  difficulties  of  measurement  under  arid 
conditions.  In  fact,  it  has  been  the  writer's  experience  that  satisfac- 
tory results  with  specially  designed  equipment  could  be  obtained  from 
observations  extending  over  2  years,  although  a  period  of  3  years  is 
preferable.  Furthermore,  the  area  from  which  evaporation  occurs  and 
the  depth  to  ground-water  at  various  points  within  it  are  not  subject 
to  wide  fluctuations,  and  are  easily  measured.  The  determination 
of  the  rate  of  recharge  of  underground  reservoirs  of  the  basin  type, 
therefore,  is  a  problem  of  soil  evaporation,  transpiration,  and  stream 


154  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

flow,  all  of  which  processes,  with  the  exception  of  transpiration  from 
trees,  are  now  capable  of  measurement  with  relative  accuracy  at 
reasonable  cost. 

The  general  method  pursued  in  the  Owens  Valley  studies  was  to 
ascertain,  by  extended  fic4d  measurements  of  soil  evaporation,  transpira- 
tion, and  spring  discharge,  the  average  rate  of  outflow  from  the  basin. 
All  available  evidence  seemed  to  indicate  that  the  basin  was  closed, 
so  that  the  rate  of  outflow  equalled  the  rate  of  inflow  or  recharge. 
As  a  check,  therefore,  the  rate  of  inflow  into  this  basin  from  precipi- 
tation, stream  flow,  and  irrigation  was  also  determined.  The  data 
are  presented  under  the  following  headings:  Physical  Features,  Pre- 
cipitation, Stream  Flow,  Evaporation  and  Transpiration,  Ground- 
water, and  Eate  of  Recharge  by  Percolation. 

Physical  Features. 

General. — The  Owens  Valley  lies  in  east-central  California,  along 
the  western  border  of  the  Great  Basin,  and  at  the  base  of  the  steep 
slope  of  the  Sierra  Nevada  Mountains,  as  shown  by  Fig.  1.  Including 
a  northern  extension,  known  as  Long  Valley,  its  length  is  120  miles, 
and  its  width,  from  crest  to  crest  of  confining  mountain  ranges,  varies 
from  15  to  40  miles.  The  total  area  of  the  valley  and  its  tributary 
mountain  drainage  is  about  3  300  sq.  miles,  of  which  1  200  sq.  miles 
are  desert  mountains  from  which  the  run-off  is  negligible,  536  sq. 
miles  comprise  the  Sierra  Nevada  slope,  which  yields  a  large  run-off, 
and  1 580  sq.  miles  are  the  transition  slope  and  valley  floor,  from 
which  very  slight  surface  run-off  occurs.  The  elevation  of  the  valley 
floor  varies  from  8  000  to  3  570  ft.  above  sea  level,  the  latter  being 
at  Owens  Lake,  the  lowest  depression  of  the  valley.  The  average 
elevation  of  the  crest  of  the  Sierra  Nevada  is  12  500  ft.,  with  many 
peaks  exceeding  this  elevation  by  more  than  1  500  ft.  The  White  and 
Inyo  Mountains,  a  desert  range  bordering  the  valley  on  the  east,  have 
an  average  elevation  of  10  000  ft.,  with  peaks  reaching  13  000  ft. 

The  valley  is  a  deep  structural  trough  filled  with  porous  alluvial 
material  derived  principally  from  the  Sierra  Nevada,  and  inclosed 
by  impervious  rock  formations.  The  steep  east  face  of  the  Sierra 
Nevada  is  the  result  of  faulting  accompanied  by  elevation  and  west- 
ward tilting  of  a  great  crusted  block.  The  drainage  system  of  the 
valley  consists  of  a  trunk  stream,  Owens  River,  fed  by  approximately 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


155 


Fig.  1. 


156 


SAFE   YIELD   OF    UNDERGROUND   RESERVOIRS 


forty  tributaries  entering  at  fairly  regular  intervals  from  the  west. 
The  river  terminates  in  Owens  Lake,  an  alkaline  body  of  water  without 
outlet  which  disposes  of  all  surplus  surface  water  from  the  valley  by 
evaporation.  Irrigation  is  necessary  for  the  production  of  crops,  and 
water  is  diverted  in  canal  systems  from  Owens  River  and  tributary 
streams. 

Independence  Basin. — The  portion  of  Owens  Valley  which  is  the 
subject  of  this  study  will  be  spoken  of  as  the  Independence  Basin 
(Plate  I).  It  lies  in  the  south-central  part  of  the  valley,  embracing 
with  its  tributary  drainage  area  the  region  between  the  Sierra  Nevada 
crest  and  Owens  River,  lying  between  Poverty  Hills  on  the  north 
and  Alabama  Hills  on  the  south.  These  latter  are  secondary  ranges 
extending  into  the  valley  from  the  Sierra  Nevada  and  isolating  a 
portion  of  the  valley  fill  about  25  miles  long  and  from  6  to  8 
miles  wide. 

For  the  purpose  of  this  study,  the  surface  of  the  region  has  been 
classified  as  high  mountain  drainage,  intermediate  mountain  slopes, 
outwash  slope,  and  valley  floor.     (Table  1  and  Plate  I.) 

TABLE  1. — Subdivisions  of  Independence  Region. 


Area. 

BOUKDARY. 

0) 

MI  _• 

Character  of 

Subdivision. 

U   CA 

ij  03 

Slope.     '    N'egetation. 

surface. 

iHo 

Upper. 

Lower. 

="8 

©  o 

High  mountain 

96.0 

27 

Sierra 

Mouth   of 

Precipi-  Isolated  forest 

Bare      granite 

drainage. 

crest. 

canyon. 

tous     to      trees, 
gentle,      i 

and  f  r  a  g- 
mental  rock 
a  c  c  u  m  u  la- 
tions. 

I  n  t  e  r  m  ediate 

29.4 

8 

Canyon 

6  500    ft.  ,2  000 to 3 000  Desert   bushes 

F  r  a  g  m  e  n  tal 

mountain 

drainage. 

contour. 

ft.  to  the     and  nut  piue. 

and      finely 

slope. 

mile. 

disintegrated 
rock  accumu- 
lations. 

Outwash  slope. 

165.3 

46 

6  500 -ft. 

Grass  land . 

300  to  600  Desert  bushes. 

Boulders,  sand 

contotir. 

ft.  to  the 
mile. 

and  gravel 

Vallev  floor: 

Cultivated 

4.7 
45.1 

1 
13 

Gentle 

Gentle  to 

Alfalfa,  etc.... 
Salt  grass,  etc. 

Soil. 

Soil. 

Alkali 

2.7 
13.9 

] 

level. 

Level 

Level 

None 

Soil. 

Desert 

4 

Desert  bushes. 

Fine  sand. 

857.1 

100 

SAFE    YIELD   OF    UNDERGROUND   RESERVOIRS 


157 


The  high  mountain  drainage  embraces  the  eastern  slope  of  the 
Sierra  Nevada  and  consists  of  a  series  of  seventeen  small  canyons 
which  are  the  drainage  basins  of  streams  tributary  to  Owens  River 
(Table  2).  These  canyons  are  all  narrow  at  the  mouth  (the  6  500-ft. 
level)  and  broaden  out  more  or  less  toward  the  summit,  presenting 
a  roughly  triangular  shape.  They  are  separated  by  high  knife-edge 
ridges,  which  terminate  in  triangular  slopes  facing  the  valley.  They 
have  been  cut  by  water  erosion  and  sculptured  by  active  glaciation 
above  the  7  500-ft.  level,  their  upper  portions  being  well-developed 
glacial  cirques.  In  many  places  below  the  cirques  are  series  of  benches 
occupied  by  glacial  lakes  or  meadows.  Most  of  the  cirque  floors  are 
buried  beneath  morainal  accumulations;  some  of  the  polished  canyon 
bottoms  between  the  11  500  and  8  000-ft.  levels  are  swept  clean  of 
debris,  and  others  are  completely  buried  by  morainal  material.  Ter- 
minal and  lateral  moraines  of  considerable  size  occupy  the  canyon 
floors  between  the  8  000  and  7  000-ft.  levels. 


TABLE  2. — High  Mountain  Drainage  Areas  of  Independence  Eegion. 


Arba. 

Elevation. 

Shape. 

* 

Creek. 

9 

rt  3  » 

a 

=  §<= 

in 

0-  — ' 

o 

3  H  » 
O  t8<« 

o 

Remarks. 

r.i6 

4.97 

2.48 

3.88 
7.64 
2. -35 
2.62 

8.08 

7.28 
8.42 
4.29 
4.22 
12.29 

4.01 

2.90 

9.10 
4.38 

60 

69 

65 

51 
44 
20 
.55 
65 

57 
74 
47 
43 
66 

43 

41 

74 

58 

12  000 

12  500 

12  000 

12  000 
12  000 

11  500 

12  000 
12  500 

12  500 

13  000 
13  000 
13  000 
13  500 

13  500 

13  000 

13  500 
13  000 

6  500 
6  500 
6  500 

6  000 

5  000 

6  000 
6000 
6  000 

6  000 
6  500 
6  500 
6  300 
6  500 

6  300 

6  300 

6  500 

7  000 

Triangular... 

Triangular... 

Triangular... 

Rectangular. 
Rectangular. 

Irregular 

Irregular 

Irregular 

Irregular 

Triangular... 

Irregular 

Triangular... 
Triangular... 

Irregular 

Irregular 

Triangular... 
Irregular 

3.34 

2.67 

1.21 

1.88 

2.75 

0.0 

0.0 

5.17 

1.06 
4.60 
1.09 
1.59 
7.95 

0.0 

0.0 

3.89 
0.67 

Morainal  deposits:  regu- 
lated run-off. 

Morainal  deposits;  regu- 
lated run-off. 

Morainal  deposits;  no  sur- 
face run-off. 

Morainal  deposits. 

Dry  Canyon 

Sawmill   

Thibaut  (N.  Fk.). 
Thibaut  (S.  Fk.).. 
Oak  (N.  Fk.) 

Oak  (S.  Fk) 

Little  Pine 

Pinyon 

Morainal    deposits;    regu- 
lated run- off. 

Shepard 

5.68  miles  of  crest  south  of 
Kingb-Kern  divide. 

Lies  on  east  face  of  Mount 
Williamson. 

Lies  on  east  face  of  Mount 
Williamson. 

Bairs  (N.  Fk.).... 
Bairs  (S.  Fk.).... 
George 

Hogback 

95.97 

55 

37.87 

158 


SAFE    YIELD   OF   UNDERGKOUND   RESERVOIRS 


The  intermediate  mountain  slopes  (Fig.  2)  are  the  triangular  areas 
terminating  the  ridges  between  the  canyons,  and  probably  represent 
the  original  face  of  the  range  before  it  had  been  actively  eroded  (Table 
3).  Their  lower  boundary  has  been  arbitrarily  placed  at  the  6  500-ft. 
contour,  and  their  apexes  reach  a  maximum  elevation  of  about  12  000 
ft.  They  have  a  steep  uniform  slope  of  from  2  000  to  3  000  ft.  to  the 
mile,  and  in  general  are  covered  with  a  mantle  of  disintegrated  rock 
and  slide  material  which  merges  into  the  valley  fill. 

TABLE  3. — Intermediate  Mountain  Slopes  of  Independence  Region. 


Adjoining  high 

mountain  drainage 

areas. 


Area,  in 
square 
miles. 


Elevation. 


Apex, 
in  feet. 


Center 
of  area, 
in  feet. 


Lower 
border, 
in  feet. 


Distance 
from 
Sierra 

crest  to 
center 

of  area, 

in  miles. 


Remarks. 


Tuiemaha , 

Red  Mountain , 

Taboose 

Goodale 

Division 

Sawmill 

Thibaut  (North  Fork) 
Thibaut  (South  Fork), 


Oak  (North  Fork). 
Oak  (South  Fork). 
Little  Pine 

Pinyon 

Symmes 

Shepard 

Bairs  (North  Fork) 
Bairs  (South  Fork) 

George 

Hogback  (one-half) 


2.17 
2.37 
3.94 
2.29 

0.95 
1.32 
0.53 

0.07 


3.62 
1.03 
2.02 


2.89 
0.42 


0.97 
0.48 
T.21 
2.09 
1.08 


(11  000) 
(12  000) 
12  200 
11  800 

9  500 
10  200 
10  500 

7  000 


12  600 

10  600 

11  800 


11  500 
9  200 


9  900 
9  100 

10  300 

11  200 
10  800 


8  000 
8  300 
8  000 
7  200 

7  .500 
7  500 
7  500 
6  700 


7  100 
7  100 
7  400 


7  600 
7  400 


7  200 
7  100 

7  800 

8  100 


6  500 
6  500 
6  500 
6  500 

6  500 
6  500 
6  500 
6  500 


6  500 
6  500 
6  500 


6  500 
6  500 


6  500 
6  .500 
6  500 
6  .500 
6  500 


3.0 
3.0 
3.3 

2.6 

3.5 
3.2 
3.1 
4.0 


4.2 
3.8 

3.8 


2.7 
3.2 


4.5 
5.0 
4.6 
3.5 
4.1 


Does  not  include 
Dry  Canyon. 


Charlies  Canyon 
yields  run-off  in 
normal  and 
above  normal 
years. 


Lime  Fork  yields 
run-off  in  nor- 
mal and  above 
normal  years. 

North  Fork  sim- 
ilar to  Lime 
Fork. 


29.45 


The  outwash  slope  (Fig.  2)  is  the  desert  portion  of  the  sur- 
face of  tlie  valley  fill,  extending  from  the  6  SOO-ft.  contour  at 
the  base  of  the  Sierra  Nevada  to  the  upper  edge  of  grass  and  irri- 
gated land  in  the  valley  (3  900  to  4  000  ft.).  Its  surface  is  composed 
of  loose  boulders,  gravel,  and  sand,  deposited  during  past  ages  by 
torrential    streams   coming   from   the   mountains.      This   deposit   is   of 


SAFE   YIELD   OF    UNDERGKOUXD   RESERVOIRS  IGl 

unknown  depth,  and  lies  on  a  buried  ancient  rocky  surface,  the  higher 
hills  of  which  appear  above  the  present  surface  as  buttes  or  knolls.  The 
channels  of  streams  draining  the  mountain  canyons  cross  this  slope 
in  trenches,  which,  near  the  mountains,  are  from  25  to  50  ft.  deep. 

The  valley  floor  embraces  the  area  between  the  outwash  slope  and 
Owens  River,  and  its  surface  may  be  classified  as  irrigated  land,  grass 
or  meadow  land,  alkali  land,  and  desert.  The  upper  edge  has  a 
maximum  slope  of  about  120  ft.  to  the  mile,  but  within  a  short  distance 
it  merges  into  the  practically  level  valley.  The  surface  is  soil  to  a 
depth  of  from  1  to  3  ft.,  except  on  the  desert  land,  where  it  is  fine  sand. 
Most  of  the  irrigated  land  is  along  the  upper  margin  of  the  valley  floor 
adjoining  the  creek  channels.  The  grass  or  meadow  lands  lie  between 
and  to  the  east  of  the  ranches,  and  extend  well  out  into  the  level 
valley.  The  growth  is  most  luxuriant  in  the  spring  zone,  which  is 
about  i  mile  wide  and  is  at  the  upper  edge  of  the  valley  floor.  Here 
are  numerous  small  flowing  springs,  with  temperature  of  about  62°, 
which  start  the  meadow  grass  early  in  the  season  and  keep  it  green 
until  late  in  the  autumn.  Farther  out  in  the  valley,  the  salt  grass 
makes  a  green  carpet  from  May  until  late  July.  In  the  salt-grass  land 
there  is  always  a  deposit  of  alkali  about  the  plant  roots,  and  the  soil 
surface  is  crusted.  The  spring  zone,  however,  is  free  from  alkali. 
The  worst  alkali  land  is  practically  bare  of  vegetation  and  is  thickly 
crusted  with  white  salts.  It  lies  in  the  more  level  areas  in  the  center 
of  the  valley. 

The  desert  area  to  the  east  of  Owens  River  yields  no  appreciable 
run-ofl,  and,  owing  to  its  light  precipitation,  it  makes  no  contribution 
to  the  ground-water. 

The  alluvial  material  which  forms  the  valley  fill  varies  in  size  from 
large  boulders  to  fine  clay,  and,  in  arrangement,  from  a  thorough 
mixture  of  all  sizes  to  layers  of  well-assorted  gravel,  sand,  and  clay. 
The  transporting  medium  was  water,  both  mountain  streams  and 
Owens  River  taking  part  in  the  work.  Some  of  the  material  was 
deposited  in  the  beds  and  on  the  sides  of  shifting  stream  channels, 
and  much  of  the  finer  sand  and  clay  was  deposited  from  the  quiet 
waters  of  a  large  lake  which  occupied  the  lower  portion  of  the  valley. 
The  structure  of  the  valley  fill,  therefore,  is  complex,  and  the  character 
of  the  alluvial  material  underlying  a  given  locality  is  difficult  to  de- 
termine without  actual  examination  from  borings. 


1G2  SAFE    YIELD   OF   UNDERGROUND   RESERVOIRS 

A  number  of  borings,  ranging  in  depth  from  250  to  500  ft.,  have 
been  made  in  the  basin  by  the  City  of  Los  Angeles,  in  connection  with 
the  development  of  the  aqueduct  supply.  In  general,  the  materials 
encountered  were  clay,  sand,  and  coarse  gravel  in  layers  varying  in 
thickness  from  a  few  inches  to  150  ft.  Coarse  material  in  thin  layers 
interbedded  with  clay  predominates  along  the  upper  edge  of  the  val- 
ley floor  in  the  spring  belt.  All  wells  in  this  belt  yield  Artesian  flows 
of  from  1  to  2  sec-ft.  The  material  is  progressively  finer  and  occurs 
in  thicker  strata  east  of  this  belt,  toward  the  center  of  the  valley,  and 
the  Artesian  flows  decrease  in  volume.  Near  Owens  River,  fine  sand 
and  clay  in  alternate  layers  is  the  only  material  encountered  above 
the  300-ft.  depth. 

The  streams  from  the  Sierra  Nevada  were  by  far  the  most  active 
in  the  work  of  building  up  the  valley  fill.  Their  loads  were  acquired 
in  the  mountain  canyons  and  carried  out  into  the  valley,  where  they 
were  dropped  in  order  of  size  as  the  velocity  of  flow  decreased.  The 
old  lake  level  stood  at  an  elevation  of  about  3  790  ft.  for  a  long  period, 
as  shown  by  beach  lines  on  the  east  slope  of  the  Alabama  Hills.  The 
present  3  790-ft.  contour  lies  near  the  spring  and  Artesian  belt.  The 
finer  materials  between  the  spring  belt  and  Owens  River  are  evidently 
lake  deposits.  The  ancient  lake  was  contemporaneous  with  other 
geologic  lakes  of  the  Great  Basin,  such  as  Lakes  Bonneville  and 
Lahontan.  The  geologic  history  of  these  lakes  shows  many  wide  fluc- 
tuations of  water  level,  covering  long  periods  of  time.  The  inter- 
bedding  of  fine  and  coarse  material  encountered  in  the  spring  belt 
is  evidently  the  result  of  such  fluctuation,  as  the  sudden  checking  of 
the  velocity  of  a  stream  on  entering  a  body  of  still  water  results  in 
the  immediate  deposition  of  coarse  material.  The  Artesian  and  spring 
conditions,  therefore,  result  from  hydrostatic  pressure  on  the  water 
entrapped  in  these  wedges  of  coarse  material. 

Two  cross-sections  of  the  valley,  showing  the  probable  geologic 
structure,  were  constructed  along  the  Thibaut  and  Independence  Sec- 
tions (Fig.  5).  The  topography  for  these  sections  was  obtained  from 
the  U.  S.  Geological  Survey's  map  of  the  Mount  Whitney  quadrangle, 
and  the  character  of  the  surface  material  was  determined  by  field 
inspection.  The  exposed  slopes  of  bed-rock  on  each  side  of  the  valley 
were  joined  beneath  the  valley  floor,  and  the  arrangement  of  the 
material  filling  the  basin  thus   formed  was   represented   according  to 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


163 


Elevation  above  Sea  Level,  in  Feet 


Elevation  above  Sea  Level,  In  Feet.    ^ 


o    z 

■      o  si- 


164  SAFE    YIELD   OF   UNDERGROUND    RESERVOIRS 

the  best  available  knowledge,  the  strata  of  fine  material  being  indicated 
by  solid  black.  On  the  diagram,  the  greatest  depth  of  alluvial  filling 
measures  2  500  ft.  in  the  Independence  Section,  and  1  800  ft.  in  the 
Thibaut  Section.  Two  of  the  aqueduct  wells  near  the  Independence 
Section  reached  depths  of  500  ft.  in  alluvial  material,  and  a  well 
drilled  by  the  Southern  Pacific  Company,  opposite  the  Alabama  Hills 
-at  Lone  Pine  Station  has  reached  a  depth  of  832  ft.,  entirely  in  fine 
sand.  There  is  no  reason  to  suppose  that  the  gravel  filling  near 
Independence  is  less  than  2  000  ft.  in  depth. 

The  volume  of  void  space,  or  porosity,  of  a  body  of  alluvial  mate- 
rial of  this  type  is  variously  estimated  by  different  authorities  at  from 
20  to  35%  of  the  total.  Samples  of  the  mixed  gravel,  sand,  and  silt 
of  the  outwash  slopes  west  of  Independence  were  removed  to  a  depth 
of  4  ft.,  without  disturbing  the  natural  arrangement  of  the  particles, 
and  weighed  dry  and  after  saturation.  The  results  of  these  tests  indi- 
cate a  porosity  of  28%  for  these  samples.  The  presence  of  very  coarse 
gravel  and  boulders  in  this  material  would  reduce  the  porosity,  and, 
for  the  valley  fill  as  a  whole,  25%  is  probably  more  nearly  correct. 

Precipitation. 

The  plan  followed  in  the  study  of  precipitation  was  to  gather  and 
assemble  data  from  which  to  prepare  isohyets  for  the  basin.  These 
appear  on  Plate  I,  and  are  based  on  the  available  precipitation  data 
and  an  intimate  knowledge  of  the  local  topography  and  vegetation. 

Observations  of  precipitation  were  made  in  the  Independence  Basin 
as  early  as  1865,  under  the  direction  of  United  States  Army  officers 
stationed  at  Fort  Independence.  The  record  extends  unbroken  from 
September,  1866,  to  August,  1877,  and  was  obtained  under  conditions 
sufficiently  similar  to  permit  of  combining  it  with  the  more  recent 
Weather  Bureau  record  at  Independence.  The  latter  covers  the  periods 
from  September,  1892,  to  August,  1895,  and  from  September,  1898, 
to  August,  1910,  so  that  there  are  26  seasons  for  which  precipi- 
tation records  are  available  at  Independence.  To  supplement  this 
record,  twenty  standard  Weather  Bureau  rain  gauges  were 
established,  and  observations  were  made  during  the  seasons  1908-09 
and  1909-10  (Plate  I).  These  gauges  were  distributed  sys- 
tematically over  the  valley  floor  and  outwash  slopes,  and  could  all  be 
reached  during  one  day  by  three  mounted  observers  stationed  at  points 


PLATE   I. 

TRANS.  AM.  SOC.  CIV.   ENGRS. 

VOL.  LXXVIII,  No.  1315. 

LEE    ON 

YIELD  OF  UNDERGROUND  RESERVOIRS. 


n 


r 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  165 

in  the  valley  where  shelter  was  available.  Four  records  were  also 
available  in  Owens  Valley,  outside  of  the  Independence  Basin,  at 
Bishop,  Lone  Pine,  Laws,  and  Keeler.  The  Bishop  and  Lone  Pine 
records  are  kept  by  co-operative  Weather  Bureau  observers,  and  cover 
15  and  5  years,  respectively.  The  Laws  and  Keeler  records  are  kept 
by  railroad  agents,  and  are  for  13  and  24  years. 

The  distribution  of  total  precipitation,  with  respect  to  geographic 
location,  in  the  Independence  Basin  and  adjoining  areas  depends 
to  a  great  extent  on  topographic  features,  notably  mountain  ranges 
and  valleys,  although  a  consistent  variation  is  also  evident  with  changes 
in  latitude.  The  controlling  topographic  feature  is  the  Sierra  Nevada, 
which  has  a  general  northwest  and  southeast  trend. 

This  relation  of  precipitation  and  topography  is  well  shown  by 
studying  observations  made  along  cross-sections  of  the  Sierra  Nevada 
laid  out  at  right  angles  to  the  trend  of  the  range.  Two  such  sections 
are  indicated  on  Fig.  1  as  the  Central  Pacific  and  Mokelumne  Sections. 
The  relations  of  mean  annual  precipitation,  altitude,  topographic  posi- 
tion, and  profiles  of  ground  surface  are  presented  graphically  for  the 
two  sections  in  Diagrams  1  to  6  of  Plate  11.  The  marked  similarity 
in  the  curves  for  the  two  sections  indicates  that  the  quantity  of  pre- 
cipitation at  points  in  a  transverse  section  of  the  range  conforms  to 
some  general  law.  Elevation,  obviously,  is  not  the  controlling  factor, 
for  above  the  5  000-ft.  level  the  precipitation  decreases  with  increase 
in  altitude.  The  slope  of  the  ground  surface  appears  to  be  the  most 
important  element  involved,  as  is  seen  from  Diagrams  2,  3,  5,  and  6 
of  Plate  II.  The  phenomenon  results  from  the  condensation  of 
aqueous  vapor  due  to  adiabatic  cooling  of  masses  of  moist  air  driven 
up  the  slope  of  a  mountain  range  by  the  prevailing  winds.  The  region 
of  maximum  precipitation  is  at  the  lower  cloud  limit  on  the  windward 
slope  of  the  range,  and  above  this  the  latent  heat  liberated  by  con- 
densation raises  the  temperature  above  the  dew  point,  resulting  in 
decreased  precipitation.  After  crossing  the  summit  of  a  high  range, 
the  descending  mass  of  air  contracts  in  volume,  thereby  raising  the 
temperature  rapidly  above  the  dew  point  and  resulting  in  marked  de- 
crease of  precipitation. 

The  increase  of  precipitation  with  elevation  was  first  observed  by 
Mr.  S.  A.  Hill,*  in  studying  rainfall  in  the  northwest  Himalayas  of 

*  "California  Hydrography,"  by  J.  B.  Lippincott,  M.  Am.  Soc.  C.  E.,  Water  Supply 
Paper  No.  81,  U.  S.  Geological  Survey,  p.  354. 


166  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

India,  and  he  developed  for  that  region  the  empirical  formula, 
5  =  1  -f  1.92h  —  OAOh-  +  0.02h\  in  which  R  represents  the  quantity 
of  rain  and  h  the  relative  height,  in  units  of  1  000  ft.,  above  an  assumed 
plane  which  is  itself  1  000  ft.  above  sea  level.  This  equation,  when 
platted,  gives  a  curve  very  similar  to  that  shown  in  Diagrams  1  and  4 
of  Plate  II,  the  plane  of  maximum  rainfall  being  4  160  ft.  above  sea 
level.  The  equation  does  not  apply  to  conditions  on  the  leeward  slope 
of  a  range,  however,  to  judge  by  the  discontinuity  at  the  crest  line 
shown  on  the  Sierra  Nevada  curves.  The  straight-line  relation  be- 
tween precipitation  and  elevation,  which  is  often  assumed  in  engineer- 
ing computations,  thus  appears  to  have  a  very  limited  use,  and  to  be 
at  best  a  rough  approximation. 

The  Los  Angeles  Aqueduct  precipitation  stations  in  Owens  Valley 
lie  in  three  groups,  indicated  on  Fig.  1  and  Plate  I,  as  the  Taboose, 
Oak,  and  Pairs  Sections.  The  2-year  records  for  these  stations  were 
reduced  to  averages  by  comparison  with  the  26-year  record  at  Inde- 
pendence. The  platted  curves  for  these  sections  (Plate  11)  are  all 
similar  in  shape,  and  agree  with  the  desert  slope  portion  of  the  Cen- 
tral Pacific  and  Mokelumne  curves.  The  highest  point  on  each  of  the 
Owens  Valley  curves  was  obtained  from  the  measured  run-off  of  the 
'  canyons  crossed  by  the  section  and  a  run-off  factor  chosen  after  care- 
ful study  of  precipitation  and  run-off  data  for  Kings  Eiver,  which 
drains  the  slope  of  the  Sierra  Nevada  to  the  west.  The  precipitation 
at  the  mouth  of  the  canyons  was  known  from  the  rain  gauge  observa- 
tions, and  the  average  precipitation  over  each  canyon  from  the  run- 
off. Most  of  these  canyon  drainage  areas  are  isosceles  triangles  in 
plan,  the  base  being  along  the  crest  of  the  mountains.  Also,  judging 
by  the  Central  Pacific  and  Mokelumne  Sections,  the  precipitation  in- 
creases uniformly  from  the  base  of  the  mountains  on  the  desert  side 
to  the  summit.  Hence,  the  precipitation  at  the  center  of  area  of  each 
drainage  basin  is  equal  to  the  average  precipitation  over  the  whole 
area,  and  the  precipitation  at  the  summit  is  obtainable  by  a  simple 
proportion. 

Preliminary  to  the  establishment  of  isohyets  or  lines  of  equal  an- 
nual precipitation  for  the  Independence  Basin,  a  broad  study  of  pre- 
cipitation was  made  for  the  whole  Sierra  Nevada  range  from  Lake 
Tahoe  to  the  Mojave  Desert  (Fig.  1).  This  was  based  on  the  Cali- 
fornia Water  and  Forest  Association  rainfall  map  of  the  State,  pre- 


PLATE  II. 

TRANS.   AM.  SOC.  CIV.   ENGRS. 

VOL.  LXXVIII,  No.  1315. 

LEE  ON 

YIELD  OF  UNDERGROUND  RESERVOIRS. 


WING  THE 

RAPHIC  LOCATia 

SIERRA  NEVADA  MTS 

BOOSE  GROUP  OF  P.  BAIRS  GROUP  OF  PRECIPITATION  GAUGES. 

VINO.  7.-  RELATIONOFj  DIAGRAM  NO.  13.- RELATION  OF  ALTITUDE  AND  PRECIPITATION. 


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DIAGR  diagram  NO.  14. 

ION  OFTOPOGRAPHICI  m  RELATION  OF  TOPOGRAPHIC  LOCATION  AND  PRECIPITATION. 


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SAFE    YIELD   OF    UNDERGROUND    RESERVOIRS  1G7 

pared  in  1900,  as  revised  between  American  and  Kings  Rivers  by 
Edwin  Duryea,  Jr.,  M.  Am.  Soc.  C.  E.,  in  1908.  With  all  available 
rainfall  data  to  date,  including  the  Los  Angeles  Aqueduct  and  several 
private  records,  the  writer  has  made  further  revisions  over  the  South- 
ern Sierra  and  Owens  Valley.  The  Water  and  Forest  Association  iso- 
hyets,  as  amended  by  Mr.  Duryea,  appear  on  Fig.  1  as  solid  lines,  and 
revisions  proposed  by  the  writer  are  represented  by  dotted  lines. 
Isohyets  are  shown  with  greater  detail  for  the  Independence  Basin  on 

Plate  I.  Q  T, 

Stream  Flow. 

Stream  flow  data  essential  to  the  determination  of  inflow  and  out- 
flow for  an  underground  reservoir,  are  the  run-oflf  from  precipitation, 
the  seepage  from  or  into  stream  channels,  and  the  flow  of  springs. 
Precipitation  which  finds  its  way  into  surface  streams  without  ab- 
sorption may,  along  some  portion  of  the  channel,  percolate  into  porous 
gravels  and  join  the  subterranean  supply.  On  the  other  hand,  water 
may  escape  from  the  underground  reservoir  by  seepage  into  stream 
channels  where  the  general  water  plane  is  at  a  higher  elevation  than 
mean  water  level  in  the  stream.     Escape  may  also  occur  from  springs. 

The  problem  in  the  Independence  Basin  was,  first,  to  classify  the 
surface  as  to  run-off  characteristics  and  determine  the  run-off  from 
each  subdivision;  second,  to  ascertain  seepage  losses  from  the  seven- 
teen tributary  mountain  streams  between  the  canyon  mouths  and 
the  valley  floor;  third,  to  determine  the  flow  of  springs  which  repre- 
sent water  escaping  from  the  basin;  and  fourth,  to  ascertain  whether 
Owens  River  made  or  lost  water  in  passing  through  the  basin. 

Run-ojf. — It  was  early  observed  that  the  run-off  characteristics  of 
the  four  areas  into  which  the  region  was  classified  for  study  (Table  1) 
were  similar. 

The  clay  soils  of  the  valley  floor  occasionally  yield  a  small  run-off 
during  and  following  winter  precipitations  of  1  in.  or  more  in  24 
hours,  or  warm  rain  falling  on  old  snow.  This  water  gathers  and  passes 
off  into  Owens  River  within  a  few  hours  by  way  of  four  waste  chan- 
nels. A  study  of  the  available  data  shows  that  the  average  total  run- 
off from  precipitation  on  the  valley  floor  is  about  2  sec-ft.  of  continu- 
ous flow. 

The  outwash  slopes  yield  no  appreciable  surface  run-off,  on  ac- 
count of  the  porous  gravel  formation  and  the  great  depth  to  ground- 


168  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

water.  This  fact  has  been  established  by  repeated  observations  dur- 
ing and  after  rainstorms  and  thaws,  and  is  confirmed  by  the  notice- 
able absence  of  recent  drainage  channels  or  washes,  except  those  of 
streams  which  derive  their  water  from  high  mountain  drainage  areas. 

The  intermediate  mountain  slopes  yield  a  small  run-off  during  May 
and  June,  when  the  temperature  at  that  level  is  sufficient  to  melt  the 
accumulated  winter  snow,  but  the  small  streams  do  not  advance  far 
over  the  outwash  slopes  before  they  are  entirely  absorbed.  If  the  pre- 
cipitation of  the  preceding  winter  is  below  normal,  the  snow  melts 
before  the  hot  weather  comes,  and  is  absorbed  at  once.  Springs  are 
common  along  the  lower  borders  of  these  slopes,  the  source  being  the 
melted  snow  absorbed  by  the  porous  material  above  and  brought  to  the 
surface  where  it  comes  into  contact  with  impervious  formations.  In 
only  a  few  places  does  such  water  find  its  way  into  living  streams. 

The  high  mountain  drainage  areas  have  an  abundant  run-oS,  and 
perennial  streams  flow  from  all  but  one  of  them.  The  source  of  this 
water  is  precipitation,  in  the  form  of  snow  and  rain,  which  falls  within 
the  drainage  areas,  and  to  a  small  extent  snow  dust  carried  over 
the  summits  by  the  prevailing  west  and  northwest  winds  of  winter 
and  spring.  For  all  practical  purposes,  the  average  discharge  at  the 
mouth  of  the  canyon  represents  the  average  precipitation  within  the 
drainage  area  minus  losses  by  evaporation  from  exposed  snow  sur- 
faces.    The  underflow  from  these  areas  is  negligible. 

Stream  discharge  from  the  canyons  is  at  a  minimum  from  Septem- 
ber to  April.  The  flow  during  these  months  is  remarkably  uniform, 
and  is  entirely  uninfluenced  by  the  current  storms,  though  from  70  to 
80%  of  the  annual  precipitation  occurs  between  November  1st  and 
March  31st.  The  low-water  flow  is  derived  from  springs  and  from  the 
slow  melting  of  the  snow  layer  exposed  to  the  earth's  latent  heat. 
Streams  are  usually  frozen  over  by  November,  and  as  late  as  April 
they  flow  nearly  to  the  mouths  of  the  canyons  in  tunnels  under  the 
snow.  Between  April  1st  and  20th  air  temperatures  increase  sufficiently 
to  melt  the  snow  at  the  lower  elevations,  and  the  streams  begin  to  rise. 
There  is  an  increase  in  air  temperatures  and  stream  flow  from  this 
date  until  the  maximum  flood  crest  is  reached,  some  time  between 
June  15th  and  July  15th,  depending  on  the  quantity  of  snow  to  be 
melted.     Stream  flow  then   decreases  until  some  time   in   September, 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  169 

after  which  low  water  prevails.  About  70%  of  the  annual  run-off  of 
the  streams  occurs  during  May,  June,  July,  and  August. 

Percolation  from  Stream  Channels. — The  United  States  Geologi- 
cal Survey  gauging  stations  on  streams  draining  the  high  mountain 
areas  are  at  the  lower  edges  of  the  outwash  slopes,  just  above  the  di- 
vision boxes  which  apportion  the  water  for  use  on  the  ranches  of  the 
valley  floor.  After  leaving  its  canyon  each  stream  traverses  several 
miles  of  channel  before  reaching  the  gauging  station,  and  preliminary 
observations  in  June,  1908,  showed  that  considerable  water  (in  some 
streams  50%)  disappeared  between  the  two  points.  It  was  necessary, 
therefore,  either  to  establish  regular  gauging  stations  at  the  canyon 
mouths  and  depend  on  records  for  short  periods,  or  to  devise  some 
means  of  computing  the  run-off  from  the  high  mountain  areas  from 
the  existing  Government  records,  which  extended  over  6  years.  The 
latter  method  was  chosen,  and  the  results  have  proved  very  satisfac- 
tory. 

The  loss  from  these  stream  channels  occurs  as  percolation  into 
the  porous  alluvial  material,  direct  evaporation  from  water  surface, 
and  transpiration  from  vegetation  growing  along  the  stream  borders. 
Evaporation  and  transpiration  losses  were  too  small  to  be  detected  in 
current-meter  work.  As  the  expense  of  installing  and  maintaining 
weirs  was  prohibitive,  the  problem  resolved  itself  into  a  study  of  per- 
colation from  stream  channels. 

There  are  three  factors  to  be  considered  in  a  study  of  the  sub- 
ject :  the  rate  of  percolation,  the  area  through  which  percolation  occurs 
(the  wetted  perimeter),  and  the  period  of  time  during  which  a  given 
unit  of  water  is  exposed  (velocity  of  flow).  The  rate  of  percolation 
depends  on  (1)  the  character  of  the  channel  lining  and  the  medium 
surrounding  the  channel,  as  regards  size  of  pores  and  porosity;  (2)  the 
pressure  gradient,  depending  on  the  difference  in  level  of  the  surface 
of  the  water  in  the  channel  and  the  ground-water  surface;  and  (3)  the 
temperature  of  the  water. 

The  effect  of  an  increase  in  the  wetted  perimeter,  other  conditions 
being  the  same,  is  obviously  to  increase  the  percolation,  but  such 
change  is  accompanied  by  a  proportionally  larger  increase  in  the  ve- 
locity of  flow,  which  reduces  the  time  of  exposure  of  a  given  volume 
of  water.  The  net  result,  considering  the  total  flow,  is,  therefore,  a 
proportionally  smaller  percolation,  although  this  effect  may  be  counter- 


170  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

acted  to  a  certain  extent  by  the  scouring  of  a  non-porous  channel  lin- 
ing due  to  the  increased  carrying  power  of  the  stream.  The  whole 
matter  is  affected  by  so  many  indeterminate  conditions  that  a  general 
mathematical  analysis  is  impossible,  but,  with  these  ideas  in  view,  a 
study  was  made  of  each  channel  within  the  ordinary  range  of  tempera- 
ture and  discharge. 

The  field  work  consisted  of  making  comparative  current-meter 
measurements  at  upper  and  lower  stations  on  each  creek,  giving  proper 
allowance  of  time  for  the  passage  of  water  between  the  two  points. 
The  measurements  were  made  at  intervals  of  from  6  weeks  to  2  months, 
and  extended  over  the  period  from  June  15th,  1908,  to  September  15th, 
1909,  including  the  high-water  periods  of  wet  and  dry  seasons.  Gaug- 
ing sections  were  prepared  at  the  mouth  of  the  canyon  on  each  creek. 
Estimates  of  the  time  required  for  the  passage  of  water  between  sta- 
tions were  based  on  actual  trial  with  aniline  dye.  Very  little  fluctua- 
tion in  discharge  was  observed  in  any  of  the  creeks  between  8  a.  m.  and 
5  p.  M.,  even  in  the  high-water  period. 

The  temperature  of  the  water  as  it  issues  from  the  canyons  varies 
from  35°  to  42°  Fahr.,  in  winter,  and  from  48°  to  53°  Fahr.,  in  sum- 
mer. In  winter  the  temperature  does  not  increase  much  as  the  water 
travels  toward  the  valley.  After  leaving  the  protecting  cover  of  the 
snow  in  the  canyons  during  December  and  January  the  water  actually 
becomes  colder,  ice  prevailing  for  several  weeks.  In  summer  there  is 
an  average  increase  of  10°  between  the  stations  at  the  mouth  of  the 
canyon  and  in  the  valley. 

Several  methods  were  attempted  for  generalizing  the  results,  but 
the  most  satisfactory  was  a  graphical  one,  in  which  losses  were  platted 
as  abscissas  and  stream  discharges  as  ordinates  with  rectangular  co- 
ordinates (Plate  III). 

It  was  found  that  for  each  channel  a  straight  line  expressed  the  re- 
lation of  these  two  quantities  from  April  to  October,  inclusive.  Dur- 
ing the  remaining  5  months,  the  relation  is  not  clear,  but  the  total 
loss  is  then  so  small  that  it  can  be  obtained  by  inspection  without  af- 
fecting the  accuracy  of  the  computed  discharge  at  the  mouth  of  the 
canyon.  Total  losses  are  platted  on  the  basis  of  discharge,  both  at 
lower  and  upper  stations,  so  that,  in  correcting  the  Government  rec- 
ords to  obtain  the  true  yield  from  high  mountain  drainage  areas,  the 
quantity  desired  can  be  obtained  at  once  by  entering  on  the  X-axis 


PLATE   III. 

TRANS.   AM.  SOC.  CIV.   ENGRS. 

VOL.  LXXVIII,  No.  1315. 

LEE  ON 

YIELD  OF  UNDERGROUND  RESERVOIRS. 


H  THE  VICimXY  OF  INDEPENDENCE 


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SAFE    YIELD   OF   UNDERGEOUND   EESERVOIES  171 

the  discharge  at  the  lower  or  Government  station.  It  is  also  possible 
at  the  same  time  to  read  the  loss,  in  second-feet  to  the  mile,  from  the 
straight  line  below  the  JT-axis, 

The  diagrams  on  Plate  III  were  prepared  for  the  purpose  of  com- 
puting (1)  seepage  losses  above  the  U.  S.  Geological  Survey  gauging 
stations,  and  (2)  the  actual  yield  of  high  mountain  drainage  areas. 
In  obtaining  the  field  data,  discharge  measurements  were  made  with 
small  Price  current  meters  during  the  period,  June  to  August,  1909, 
inclusive,  covering  a  season  of  small  run-oll  and  one  of  large  run-off. 
The  accuracy  is  up  to  the  standard  for  a  stream  of  this  type.  Meas- 
urements of  medium  and  high  stages  were  difficult,  on  account  of  the 
rough  sections  and  very  high  velocities.  The  upper  gauging  station  is 
at  the  mouth  of  the  canyon,  or  below  impervious  dikes  forcing  seepage 
water  to  the  surface.  The  average  elevation  is  6  000  ft.  The  lower  sta- 
tion is  that  used  by  the  U.  S.  Geological  Survey  (unless  otherwise 
noted),  which  is  above  the  diversion  and  has  an  average  elevation  of 
4  100  ft.  Below  the  latter  there  is  i  mile  or  more  of  channel  suffering 
a  large  seepage  loss  which  is  not  included.  The  length  of  the  channel 
was  obtained  by  scaling  from  the  Mt.  Whitney  Quadrangle,  and,  for 
Taboose,  Red  Mountain,  and  Tinemaha  Creeks,  from  a  triangulation 
survey.  Elevations  were  obtained  in  a  similar  manner.  In  using  the 
diagrams,  the  straight-line  relation  applies  from  April  to  October,  in- 
clusive, during  which  time  temperature  and  discharge  vary  similarly. 
The  dotted  portions  are  not  supported  by  field  data,  and  are  to  be  used 
with  judgment.  From  November  to  March,  inclusive,  temperature  is 
the  only  effective  variable,  and  arbitrary  values  for  loss  have  been 
selected.  Line  "A"  expresses  the  relation  of  total  loss  to  discharge  at 
the  U.  S.  Geological  Survey  Station;  Line  "B"  expresses  the  same  re- 
lation at  the  mouth  of  the  canyon;  and  Line  "C"  expresses  the  loss 
per  mile  to  discharge  at  the  mouth  of  the  canyon.  The  diagrams  are 
arranged  so  that  all  the  four  values  involved  may  be  obtained  by  en- 
tering any  one  of  them. 

There  are  some  interesting  conclusions  to  be  drawn  from  these  dia- 
grams. In  general,  the  quantity  of  water  percolating  from  the  chan- 
nels studied  varies  with  the  time  of  year  and  with  different  channel 
conditions.  Variation  with  the  time  of  year  is  due  to  the  combined 
effects  of  temperature,  area  of  wetted  perimeter,  and  velocity  of  flow. 
These  work  more  or  less  in  harmony  during  April  to  October,  inclusive, 


173  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

and  produce  the  straight-line  relation  of  total  loss  and  discharge.  From 
November  to  March,  inclusive,  canyon  discharges  remain  practically 
constant,  showing  that  variations  are  largely  controlled  by  temperature. 
Discharges  are  then  so  small,  however,  that  errors  of  measurement  are 
appreciable,  and  losses  by  evaporation  have  greater  weight,  so  that  the 
true  relation  of  loss  and  temperature  does  not  appear.  A  possible 
relation  between  total  loss  and  temperature  is  suggested  by  the  results 
on  Division  Creek,  where  the  discharge  at  the  mouth  of  the  canyon 
was  practically  uniform  during  the  period  of  study.  Using  as  ordinates 
the  mean  air  temperature  at  Independence  for  the  30  days  preceding 
each  date  of  measurement,  we  obtain  a  straight  line  which  crosses  the 
A^-axis  at  about  35  degrees.  A  line  supported  by  additional  data  might 
cross  nearer  32°,  the  temperature  at  which  percolation  becomes  physi- 
cally impossible. 

The  character  of  the  surrounding  medium  was  the  only  channel 
condition  which  noticeably  affected  percolation.  The  loss  from  a 
channel  crossing  fissured  lava,  even  where  the  lava  was  covered  by  a 
thin  sheet  of  alluvium,  was  30%  greater  than  that  in  coarse  alluvium. 
The  streams  studied  do  not  overflow  their  channels,  so  that  the  effect 
of  varying  channel  slopes  and  wetted  perimeter  could  not  be  studied. 
The  run-off  from  each  mountain  canyon  was  computed  from  U.  S. 
Geological  Survey  monthly  mean  discharge  records,  by  use  of  the  dia- 
grams. The  results  are  summarized  in  Tables  4  and  5.  The  missing 
seasons  were  estimated  from  the  unbroken  records  of  neighboring 
streams  after  a  detailed  study  of  yield  per  square  mile  and  annual  de- 
parture from  normal  for  each  stream.  The  long-term  mean  discharge 
was  obtained  by  comparison  with  the  Kings  Kiver  record,  which  covered 
21  years.  This  stream  was  chosen  because  its  drainage  area  adjoined 
most  of  the  Owens  Valley  streams  and  because  conditions  affecting 
run-off  were  more  nearly  similar  than  on  any  other  stream.  The  re- 
sults indicate  that  the  total  annual  mountain  run-off  during  the  period 
of  record  was  153  annual  sec-ft.  and  the  normal  130  annual  sec-ft. 
This  total  does  not  include  Red  Mountain  and  Tinemaha  Creeks, 
which  pass  out  of  the  basin  after  crossing  a  portion  of  the  outwash 
slope.  The  normal  run-off  per  square  mile  for  streams  north  of  the 
Kings-Kern  divide  with  60%  or  more  of  area  above  10  000  ft.,  is 
1.75  sec-ft.,  and,  for  streams  similarly  situated,  with  less  than  60% 
above  10  000  ft.,  1.18.     For  streams  south  of  the  Kings-Kern  divide, 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


173 


TABLE  4. — Seasonal  Discharge,  in  Second-Feet,  at  United  States 
Geological  Survey  Stations,  of  Creeks  Tributary  to  Inde- 
pendence Region. 

(Figures  in  parentheses  are  estimated.) 


Creek. 

Year  Beginnikg  September  1st. 

Observed 
5-year 
mean. 

Com- 
puted 

1901. 

1905. 

1908. 

1907. 

1908. 

1909. 

21 -year 
mean. 

(5.7) 
(3.9; 
0 
(3.9) 

11.4 
5.4 
0 

7.3 
5.4 
(1.0) 
31. S 

28.5 

(2.8) 
23.1 
8.0 
18.6 
(1.0) 

10.3 
6.6 
0 

10.9 
(7.6> 
(1.0) 
23.9 

22.5 

3.1 
11.0 

4.8 
10.9 
(0.5) 

4.7 
3.8 
0.0 
7.6 

(5.0) 
0.8 

15.8 

11.8 

0.8 
7.2 
2.0 
6.5 
(0) 

8.6 
6.4 
0 

9.7 

7.3 

0.9 

30.8 

25.8 

6.3 
12.9 

6.1 
13.0 
(0.5) 

5.9 
5.3 
0 

9.9 
7.2 
0.2 
18.4 

17.2 

1.1 

7.7 
2.4 
6.8 
0 

8.2 
5.5 
0 

9.1 

6.5 

0.6 

24.1 

31.2 

3.8 
13.5 

4.7 
11.2 

0.4 

6.5 

4.3 

0 

7.3 

Sawmill 

5.1 

(0.5) 
(13.0) 

(10.7) 

0.5 

Oak 

19.0 

Pinyon f 

Symmes 

2.2 

9.8 

3.7 

George  

8.8 

(0) 

0.3 

144.2 

113.1 

66.0 

128.3 

83.1 

106.7 

84.0 

Percentage  of  totals  at 
mouth  of  canyon 



68 

63 

61 

66 

63 

65 

65 

TABLE    5. — Seasonal    Discharge,    in    Second-Feet,    at    Mouth    of 

Canyon,  of  Creeks  Tributary  to  Independence  Region. 

(Figures  in  parentheses  are  estimated.) 


Creek. 

Year  Beginning  September  1st. 

Observed 
6-year 
mean. 

Com- 
puted 

1904. 

1905. 

1906. 

1907. 

1908. 

1909. 

21-year 
mean. 

Taboose 

11.9 
7.6 
(3.9) 
(4.4) 
(4.0) 
(1.9) 
16.7 
10.7 
(3.6) 
(3.5) 
(11.1) 
^4.3^ 
(8.2) 
(2.8) 

19.2 

9.9 

(5.1) 

(3.9 

6.5 

(3.1) 

43.2 

24.6 

(8.9) 

(8.8) 

31.4 

11.8 

23.8 

(7.8) 

30.4 
J2.3 

(6.3) 
11.2 

9.1 
(4.4) 
33.8 
20.5 
(6.6) 

7.0 
18.9 

7.7 
16.5 
(5.7) 

9.8 
7.2 
(3.7) 
6.9 
5.5 
(2.7) 
21.2 
12.0 
(4.2) 
3.7 
13.5 
4.2 
9.8 
(4.3) 

16.0 

11.3 

(5.7) 

8.7 

7.3 

(3.5) 

42.6 

34.3 

9.3 

10.2 

3.09 

9.4 

18.7 

(6.8) 

13.4 
10.3 
(5.3) 
9.5 
7.3 
(3.4) 
35.0 
16.7 
3.5 
4.9 
14.1 
4.8 
10.3 
(3.7) 

15.0 
9.8 
5.0 
7.9 
6.6 
3.3 

30.4 

18.1 
6.0 
6.3 

18.3 
7.0 

14.6 
5.2 

13  7 

8  3 

Dry  Canyon 

4.3 

Division 

6  7 

Sawmill 

5  6 

Thibaut 

3.7 

Oak 

35.8 

Little  Pine 

15  3 

4  8 

Symmes 

5  3 

Shepard 

15  5 

Bairs 

5  9 

George 

12  4 

Hogback  

4  4 

94.6 

211.0 

180.4 

108.6 

194.5 

130.9 

153.3 

129.6 

Percentage     reaching 
U.  S.  G.  S.  Stations. 

68 

63 

61 

66 

63 

65 

65 

174  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

the  normal  run-off  is  1.36  and  0.86  sec-ft.,  respectively.  It  is  also 
of  interest  to  note  that  only  65%  of  this  run-off  reaches  the  Govern- 
ment gauging  stations. 

Springs. — The  occurrence  of  springs  in  the  basin  is  due  to  the  re- 
appearance of  water  which  originally  fell  within  its  boundaries  as 
precipitation  and  was  absorbed.  There  are,  in  general,  three  types  of 
springs  which  give  rise  to  surface  streams :  those  which  derive  their 
supply  from  precipitation  on  the  intermediate  mountain  slopes,  and 
appear  at  the  base  of  these  slopes ;  those  which  derive  their  supply  from 
precipitation  and  stream  percolation,  and  appear  along  the  upper  edge 
of  the  grass  land;  those  which  derive  their  supply  from  precipitation  on 
lava  flows,  and  appear  at  the  lower  borders  of  the  flows. 

The  springs  of  the  first  type  are  not  deep  seated ;  they  represent  the 
drainage  from  the  superficial  deposits  lying  on  the  triangular  moun- 
tain slopes  between  canyons.  The  temperature  of  their  water  is  about 
47°  or  48°  Fahr.,  and  the  flow  in  many  of  them  increases  in  early  sum- 
mer and  decreases  during  late  summer  and  autumn.  The  water  from 
most  of  these  springs  sinks  into  the  porous  gravels  of  the  outwash 
slope,  and  joins  the  main  body  of  ground-water  in  the  basins. 

The  line  of  springs  along  the  upper  edge  of  the  grass  land  repre- 
sents the  intersection  of  the  natural  surface  of  the  ground  and  the 
surface  of  the  ground-water.  The  water  has  penetrated  rather  deeply 
into  the  gravel  fill,  and  issues  with  a  temperature  of  about  62°  Fahr., 
which  is  5°  higher  than  the  mean  annual  temperature  at  Independence 
and  1°  lower  than  that  of  water  flowing  from  Artesian  wells  in  the 
same  location.  The  flow  of  these  springs  is  variable,  being  least  in 
late  summer  and  greatest  in  early  spring,  with  regular  fluctuation 
between  these  dates,  evidently  depending  on  ground-water  stages  within 
the  grass  area.  Only  during  the  winter  months  is  the  discharge  suf- 
ficient to  be  the  source  of  surface  streams  which  flow  any  considerable 
distance,  and  even  then  there  are  only  a  few  of  such  streams  which 
reach  Owens  Eiver.  Most  of  the  yield  of  these  springs  is  lost  by 
evaporation  and  transpiration.  The  winter  discharge  of  individual 
springs  varies  from  0.5  sec-ft.  down  to  a  quantity  which  is  only 
enough  to  fill  small  pools  of  standing  water,  from  which  the  evapora- 
tion equals  the  yield.  The  total  winter  discharge  from  all  these 
springs  is  about  4  sec-ft. 


SAFE   YIELD   OF   UNDEEGROUND   RESERVOIRS  175 

The  springs  issuing  from  the  lava  formations  are  unique  in  having 
uniform  discharges  throughout  the  year  and  a  temperature  of  57° 
Fahr.  The  water  is  probably  derived  from  precipitation  on  the  lava 
surface,  absorbed  by  the  porous  rock,  and,  by  reason  of  the  peculiar 
formation,  gathered  and  delivered  at  the  lower  margin  of  the  flow. 
The  largest  of  these  is  Blackrock  Springs  (Plate  I),  9  miles  north  of 
Independence.  It  has  a  discharge  of  23  sec-ft.,  which  flows  out  across 
the  valley  floor  in  two  sloughs,  each  emptying  into  a  series  of  shallow 
lakes.  From  November  to  March,  inclusive,  an  average  flow  of  about 
7  sec-ft.  reaches  Owens  River,  but  during  the  remainder  of  the  year 
all  the  water  is  lost  by  seepage,  evaporation,  and  transpiration.  Hines 
Spring  is  3  miles  north  of  this  spring,  and  has  a  continuous  yield  of 
about  4  sec-ft.  Approximately,  1  sec-ft.  finds  its  way  into  Owens 
River  during  the  winter,  but  is  lost  during  the  remainder  of  the 
year.  Campbell  Spring  is  east  of  Owens  River,  1  mile  north  of  Aber- 
deen. It  has  a  yield  of  about  0.5  sec-ft.,  and  discharges  directly  into 
the  river.  Upper  and  Lower  Seeley  Springs  are  just  above  and  just 
below  Charlies  Butte,  and  discharge  directly  into  Owens  River.  The 
upper  spring  has  a  flow  of  9.5  sec-ft.,  which  is  included  in  measure- 
ments of  Owens  River  at  the  Butte.  The  lower  one  has  a  flow  of  1.5 
sec-ft. 

Owens  River. — Owens  River  flows  lengthwise  of  the  Independence 
Basin  for  29  miles,  although  the  actual  length  of  its  channel  is  possi- 
bly 20%  greater,  owing  to  its  sinuosity.  It  is  the  drainage  outlet  for 
the  waste  surface  water  of  the  region,  including  the  run-off  from  the 
valley  floor,  the  yield  of  springs,  and  a  small  portion  of  the  run-off 
from  high  mountain  drainage  areas.  In  order  to  account  for  all  es- 
caping surface  waters,  and  determine  the  condition  of  the  river  chan- 
nel with  regard  to  seepage,  observations  of  river  discharge  were  made 
daily  near  the  north  and  south  boundaries  of  the  region,  and  meas- 
urements of  discharge  into  and  diversion  from  the  river  channel  were 
made  between  these  two  points.  Complete  data  are  available  for  1909 
and  1910.  Analysis  of  these  data  shows  that  seepage  losses  occur  dur- 
ing high-water,  and  seepage  gains  during  low-water  stages.  The  net 
result  is  a  loss  between  Charlies  Butte  and  Whitney  Bridge,  which 
can  be  accounted  for  by  channel  evaporation.  The  water  plane  of  the 
valley  on  each  side  of  the  river  lies  between  high-  and  low-water  levels 
in  the  river.     Hence,  seepage  gain  and  loss  are  the  result  of  local  ab- 


176  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

sorption  and  drainage  along  the  river  channel,  and  have  no  relation  to 
the  general  ground-water  situation  of  the  basin. 

Evaporation  and  Transpiration. 

Evaporation  from  Water  Surfaces. — Measurements  of  evaporation 
from  free  water  surfaces  were  made  under  three  conditions:  from  a 
pan  floating  in  a  body  of  water,  from  a  pan  placed  in  the  soil,  and  from 
a  deep  tank  placed  in  the  soil.  The  first  and  second  were  designed 
to  furnish  data  regarding  evaporation  from  reservoir  surfaces  and 
from  areas  of  shallow  flood  water,  respectively.  The  third  was  desired 
for  purposes  of  comparison  with  records  of  evaporation  from  soil.  The 
pans,  which  were  of  the  pattern  used  by  the  U.  S.  Keclamation  Service, 
were  3  ft.  square  and  10  in.  deep,  and  were  of  galvanized  sheet-iron. 
Observations  were  made  by  replacing  the  quantity  evaporated  with  a 
cup  having  a  capacity  equal  to  a  depth  of  0.01  in.  in  the  pan.  The 
initial  height  of  the  water  surface  was  such  that  a  pin,  projecting 
from  the  center  of  the  pan  and  remaining  at  a  fixed  height,  2  in.  be- 
low the  rim,  was  just  submerged.  The  deep  tank  was  circular,  3^  ft. 
in  diameter  and  4  ft.  deep,  and  observations  were  made  in  a  stilling 
well  with  a  hook-gauge  and  vernier  scale  reading  to  0.01  in.  The  rec- 
ords were  all  kept  near  Independence,  and  observations  were  made 
every  second  day  in  summer  and  every  fourth  day  in  winter. 

The  record  for  the  pan  in  water  (Table  6)  is  available  from  August 
4th,  1908,  to  June  1st,  1911.  The  pan.  Fig.  3,  at  first,  was  in  Black- 
rock  Slough,  but  was  moved  to  its  final  location,  in  Owens  River  at 
Citrus  Bridge,  on  May  7th,  1909.  The  pan  was  supported  by  a  timber 
float,  which  protected  it  from  splashing  water.  The  depth  of  water 
beneath  the  pan  varied  from  1  to  5  ft.,  depending  on  the  river  stage. 
The  river  water  had  a  moderate  velocity,  and  varied  in  temperature 
from  about  75°  Fahr.,  in  summer,  to  about  40°  Fahr.,  in  winter.  The 
river  banks  averaged  4  ft.  high  above  the  water  surface,  and  the  pan 
was  about  30  ft.  from  them.  Rain  gauge  No.  18  was  100  ft.  away,  on 
the  river  bank,  and  was  observed  in  connection  with  the  evaporation 
record. 

The  record  for  the  pan  in  soil  is  broken.  It  extends  from  August 
1st,  1909,  to  November  30th,  1909,  and  from  March  14th,  1910,  to 
June  1st,  1911.  The  pan,  Fig.  4,  was  in  the  valley  floor  at  the  soil 
evaporation  experiment  station,  about  3  miles  east  of  Independence. 


SAFE    YIELD   OF   UNDERGROUND   RESERVOIRS 


177 


It  was  set  in  a  shallow  excavation  with  soil  banked  up  to  about  half 
the  depth  of  the  pan.  Water  temperatures  range  from  95°  Fahr.,  in 
summer,  to  32°  Fahr.,  in  winter.  The  surface  temperature  was  about 
1°  warmer  than  that  for  the  mixed  contents  of  the  pan.  Table  7  sum- 
marizes the  results  by  months  for  this  pan,  and,  by  comparing  it  month 
by  month  with  the  evaporation  from  the  pan  in  water,  an  average  ex- 
cess of  about  33%  is  observed.  This  is  probably  due  to  the  higher 
temperature  of  the  water  in  the  pan  in  soil  during  the  hours  of  sun- 
light. 

TABLE  6. — Depth  of  Evaporation,  in  Inches,  From  Water  Surface 
Near  Independence  (Pan  in  Water). 


1908. 

1909. 

1910. 

1911. 

Average 
percent- 

Month. 

Total. 

Rate 
per  24 
hours. 

Total. 

Rate 
per  21 
hours. 

Total. 

Rate 
per  24 
hours. 

Total. 

Rate 
per '24 
hours. 

age  of 
annual 
evapora- 
tion. 

1.60 
2.40 
4.70 
7.80 
9.60 
10.10 
10.40 
8.00 
6.60 
3.90 
2.60 
(1.85) 

0.052 
0.086 
0.152 
0.243 
0.310 
0.337 
0.335 
0.258 
0.220 
0.126 
0.087 
0.C60 

1.75 
2.50 
5.15 
7.05 
8.29 
9.90 
8.50 
8.20 
6.30 
4.20 
2.36 
1.24 

0.056 
0.089 
0.166 
0.235 
0.267 
0..330 
0.274 
0.264 
0.210 
0.135 
0.079 
0.040 

1.65 
2.35 
3.70 
6.25 
8.01 

0.053 
0.084 
0.119 
0.208 
0.258 

3 

4 

March 

7 

11 

May 

13 

15 

July 

14 

*4.90 
5.30 

0.222 
0.176 

12 

Seotember 

10 

October 

3.50  1     0.113 
2,50  ;    0.0S3 
1.50        0.048 

6 

November 

4 

December 

2 

69.05 

0.189 

65.44 

0.179 

100 

*  August  lOih  to  81st,  Inclusive. 

The  deep-tank  record  extends  unbroken  from  April  16th,  1909,  to 
Dec.  31st,  1911.  The  tank.  Fig.  6,  was  at  the  soil  evaporation  experi- 
ment station,  and  was  set  in  the  soil  with  the  upper  rim  flush  with 
the  surface.  The  water  surface  was  not  allowed  to  fall  more  than  4 
in.  below  the  rim.  The  temperature  of  the  surface  water  varied  from 
80°  Fahr.,  in  the  heat  of  summer  to  freezing  in  winter.  Except  during 
freezing  weather,  the  average  temperature  of  the  contents  of  the  tank 
was  5°  less  than  that  of  the  surface  layer.  The  presence  of  the  sur- 
rounding soil  makes  the  range  in  temperature  less*  than  that  for  the 
shallow  pan.  The  record,  which  is  presented  in  Table  8,  indicates  an 
annual  depth  of  evaporation  practically  equal  to  that  from  the  pan  in 
water  at  Citrus  Bridge.     The  monthly  distribution  is  more  uniform, 


178 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


TABLE  7. — Depth  of  Evaporation,  in  Inches,  From  Water  Surface 
Near  Independence  (Pan  in  Soil). 


1909. 

1910. 

1911. 

Month. 

Total. 

Rate 

per  24 
hours. 

Percent- 
age of 
evapora- 
tion from 
pan  in 
water. 

Total. 

RatP 
per  21 
hours. 

Percent- 
age of 
evapora- 
tion from 
pan  in 
water. 

Total. 

Rate 

per  24 
hours. 

Percent- 
age of 
evapora- 
tion from 
pan  in 
water. 

2.25 
2.25 

4.80 
8.12 
10.25 

0.073 
0.080 
0.155 
0.271 
0.330 

138 

95 

*4.25 

9.50 

10.61 

11.95 

12.55 

11.80 

8.80 

5.60 

2.85 

1.60 

0.236 
0.316 
0.312 
0.398 
0.405 
0..S81 
0.293 
0.180 
0.095 
0.052 

130 

135 
128 
121 
148 
144 
140 
183 
121 
129 

130 



128 

10.70 
8.50 
5.80 
3.80 

0..34.T 
0.283 
0.187 
0.127 

134 
129 
149 
146 

September.. 
October 



133 

i 

*  Marc5i  14th  to  31st,  inclusive. 


TABLE  8. — Depth  of  Evaporation  From  Water  Surface  Near 

Independence. 

Deep  Tank  in  Soil. 


1909. 

1910. 

1911. 

a 
o 

c  5  - 

y-t 

Q-4 

®  ^  S   • 

Month. 

a   . 

a 'it 

■D.2S  t; 

2  • 

S^t 

aj.2  S  u 

a   . 

.sis 

OH 

if  Is 

a 

^OJ 

— '® 

o  a 

*  £  0 

Percent 

evapor 

from 

in  wa 

o  a 
Eh- 

5  S  o 

Percent 

evapor 

from 

in  wa 

Bis 

Percent 

evapor 

from 

in  wa 

2.00 
2.90 
5.60 
7.40 

0.064 
0.104 
0.180 
0.246 

114 
116 
109 
105 

2.30 
2.55 
3.95 
6.80 

0.074 
0.091 
0.127 
0.226 

139 

108 
107 
84 

3 

Feb 

4 

Mar 

7 

Apr 

2.90* 

0.193 

10 

May 

7.50 

0.242 

78 

7.71 

0.248 

93 

7.90 

0.254 

77 

12 

June 

7.80 

0.260 

77 

8.60 

0.287 

87 

6.65 

0.222 

11 

July 

7.90 

0.2.54 

76 

8.30 

0  268 

98 

8.60 

0.277 

12 

AuHT 

8.20 

0.264 

102 

8.80 

0.284 

107 

9.65 

0.311 

14 

Sept 

7.20 

0.240 

109 

7.30 

0.243 

116 

7.16 

0.239 

11 

Oct 

5.00 

0.161 

128 

5.15 

0.166 

123 

4.90 

0.1.58 

7 

Nov 

3.30 

0.110 

127 

3.10 

0.103 

131 

8.00 

0.100 

5 

Dec 

(2.20) 

0.071 

119 

2.15 

0.069 

173 

(2.50) 

0.081 

4 

Totals.. 

69.01 

0.188 

106 

65.96 

0.180 

100 

*  For  period,  April  16th  to  30th,  inclusive. 


Pig.    6. — Deep-Watek   Evapobation   Tank. 


PiQ.  7. — Soil,  Tank  No.  3  in  Operation. 


SAFE   YIELD   OF   UNDEEGROUND   RESERVOIRS  181 

there  being  Y0%  of  the  total  during  the  6  summer  months  and  a  differ- 
ence of  27  in.  between  summer  and  winter  evaporation.  The  effect  on 
evaporation  of  the  modified  temperature  extremes  of  the  soil  is  weU 
shown  by  comparison  with  the  record  for  the  pan  in  water  (Table  6). 
The  temperature  conditions  for  the  deep  tank  agree  closely  with  those 
of  the  surrounding  soil. 

Evaporation  from  Ground  Surface. — Water  in  the  surface  layers  of 
the  ground  is  subject  to  evaporation,  either  directly  from  the  soil  or 
through  vegetation  by  the  process  of  transpiration.  It  is  available  for 
evaporation  in  Owens  Valley  under  two  conditions:  temporarily,  fol- 
lowing a  rainstorm  or  sudden  thaw,  and  permanently,  within  areas 
where  the  average  depth  to  ground-water  does  not  exceed  8  ft.  The 
total  evaporation  under  the  first  condition  is  relatively  unimportant, 
because  of  the  infrequency  of  storms  and  the  small  quantity  of  pre- 
cipitation, and  no  attempt  was  made  to  measure  it.  Under  the  second 
condition,  however,  evaporation  losses  are  large,  for,  not  only  is  soil 
capillarity  able  to  draw  gravity  water  to  the  surface,  but  roots  of 
vegetation,  such  as  wild  grass,  penetrate  the  soil  to  ground-water  and 
become  the  channels  by  which  a  large  quantity  of  moisture  is  conveyed 
into  the  atmosphere.  Evaporation  from  bare  soil  combined  with  trans- 
piration is,  in  fact,  the  most  important  element  entering  into  computa- 
tions relating  to  ground-water  for  this  region.  So  few  data  are  avail- 
able on  the  subject  that  extended  observations  were  undertaken. 

Owens  Valley  is  an  ideal  location  for  carrying  on  such  experi- 
ments. In  the  first  place,  the  source  of  water  available  for  evaporation 
may  be  kept  under  the  complete  control  of  the  observer  as  regards  the 
quantity  and  rate  of  supply.  Storms  are  rare,  and  the  total  precipita- 
tion is  small,  so  that  little  uncertainty  exists  from  this  cause  regard- 
ing the  quantity  of  percolation  from  precipitation  on  the  surface  of  a 
body  of  isolated  soil.  Second,  the  method  by  which  the  surface  soils 
of  the  valley  floor  are  kept  moist  can  be  reproduced  artificially  on  a 
small  scale  with  only  a  slight  departure  from  natural  conditions.  The 
source  of  supply  for  soil  moisture  is  a  permanent  ground-water  sur- 
face from  which  water  is  drawn  by  capillary  forces.  This  ground- 
water is  replenished  by  percolation  from  the  precipitation  and  surface 
water  of  the  intermediate  mountain  and  outwash  slopes,  which  seeps 
laterally  toward  the  valley  floor  and  lies  beneath  it  under  hydrostatic 
pressure    sufiicient    to   maintain    a    permanent    ground-water    surface. 


183  SAFE   YIELD   OF   UNDEKGROUND   RESERVOIRS 

Similar  pressure  can  be  reproduced  in  the  bottom  layer  of  an  isolated 
body  of  soil,  and  capillary  forces  can  be  depended  on  to  raise  moisture 
to  the  surface.  Finally,  the  large  annual  depth  of  evaporation  makes 
possible  a  more  accurate  determination  of  its  quantity  than  in  a  less 
arid  region.  Experiments  carried  on  under  these  conditions  have  been 
very  satisfactory. 

The  rate  of  evaporation  from  soil  depends  on  the  temperature  of 
the  air  and  soil,  the  quantity  of  moisture  already  in  the  immediately 
surrounding  atmosphere,  the  quantity  of  moisture  in  the  surface  lay- 
ers of  the  soil,  and  the  character  of  the  vegetation  and  other  soil  cov- 
ering. The  first  two  of  these  factors  have  the  same  effect  on  soil 
evaporation  as  on  that  from  a  free  water  surface — higher  air  and  soil 
temperatures  result  in  increased  evaporation,  as  does  also  dryer  at- 
mosphere or  increased  movement  of  wind.  The  third  factor  is  di- 
rectly proportional  to  the  rate  of  evaporation,  because  the  loss  of  mois- 
ture occurs  from  soil  grains  at  or  very  near  the  surface.  The  quantity 
of  moisture  in  the  soil  available  for  evaporation  thus  depends  on  the 
character  of  the  soil,  as  regards  capillarity  and  depth  to  the  ground- 
water surface.  For  example,  in  a  coarse,  sandy  soil,  "gravity  water" 
will  be  drawn  to  the  surface  through  the  capillary  spaces  from  depths 
not  exceeding  4  ft.,  and,  in  a  fine  sandy  or  clayey  soil,  water  will  be 
drawn  from  depths  as  great  as  8  ft.  The  last  factor,  the  extent  and 
character  of  vegetation,  affects  the  evaporation  rate  both  through  the 
activity  of  transpiration  and  the  effect  on  capillarity.  Plant  roots  are 
continually  absorbing  water  from  the  soil;  this  water  passes  off  into 
the  atmosphere  through  the  leaves,  and  the  evaporation  losses  from 
soil  are  greatly  increased  thereby.  The  roots  of  native  salt  grass 
will  penetrate  to  a  depth  of  8  ft.  in  search  of  water.  A  further  effect  of 
the  growth  of  vegetation  is  to  increase  the  vertical  capillary  flow  of 
moisture  through  soil  by  way  of  the. many  tubes  filled  with  the  rotted 
fiber  of  dead  roots.  These  tubes  are  the  result  of  years  of  growth, 
and  penetrate  the  soil  in  all  directions  above  the  ground-water  surface. 

The  purpose  of  the  experiments  was  to  obtain  data  sufficiently  com- 
plete to  compute  the  total  volume  of  water  annually  lost  by  evapora- 
tion and  transpiration  from  the  valley  floor.  This  involved  making 
observations  under  the  various  local  conditions  which  affect  soil  evap- 
oration. The  plan  was  to  reproduce  natural  conditions  in  isolated 
bodies  of  typical  soil  and  determine  the  evaporation  therefrom  for 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  183 

varying  climatic  conditions,  depths  to  ground-water,  soils,  and  vege- 
tation. 

The  experimental  equipment  consists  of  two  galvanized-iron  tanks, 
6i  ft.  in  depth,  connected  at  the  bottom  by  an  18-ft.  length  of  galvan- 
ized pipe.  (See  Fig.  8.)  The  smaller  tank  is  2  ft.  4 y^.y  in.  in  diame- 
ter, and  has  a  tight-fitting  cover.  The  larger  tank  is  7  ft.  5^  in.  in 
diameter,  and  has  a  system  of  branching  perforated  pipes  at  the 
bottom  connected  with  the  pipe  from  the  smaller  tank.  The  two  tanks 
and  all  connections  are  water-tight,  and  water  poured  into  the  smaller 
or  reservoir  tank  passes  into  the  larger  or  soil  tank  and  escapes 
through  the  perforations.  These  two  tanks  were  placed  in  excavations 
of  proper  size  to  receive  them,  the  soil  tank  was  filled  with  the  exca- 
vated soil,  and  the  reservoir  tank  was  filled  with  water.  A  6-in.  layer 
of  screened  gravel,  too  coarse  to  enter  the  xV-in.  perforations,  was 
laid  in  the  bottom  of  the  soil  tank  in  order  to  insure  an  uninterrupted 
and  well-distributed  feeding  of  water  from  the  reservoir  tank  into  the 
superimposed  soil.  As  soon  as  the  material  became  saturated  and 
capillary  action  was  established  to  the  surface,  the  water  level  in  the 
soil  was  brought  to  the  desired  depth  and  kept  there  by  supplying 
water  to  the  reservoir  tank  in  measured  quantities.  Volumetric 
measurements  of  water  poured  into  or  withdrawn  from  the  reservoir 
tanks  were  made  with  an  ordinary  gallon  measure.  Accumulation  or 
depletion  of  the  supply  in  the  reservoir  tank  was  determined  volumet- 
rically  by  measuring  the  depth  of  water  with  a  steel  tape.  The  vol- 
ume passing  out  of  the  reservoir  tank  during  a  given  period  represents 
the  total  evaporation  from  the  soil  tank  during  that  period. 

The  position  of  the  ground-water  surface  in  the  soil  tank  was  de- 
termined by  measuring  its  depth  below  the  ground  surface  in  2-in. 
augur  holes  bored  in  the  soil  to  a  proper  depth.  Measurements  were 
made  from  a  fixed  point  with  a  steel  tape  weighted  at  the  end  and 
chalked  before  each  observation.  Three  holes  were  placed  in  each 
tank,  half  way  between  the  center  and  rim,  on  radii  120°  apart.  The 
holes  were  not  bored  deep  enough  to  reach  the  bottom  layer  of  coarse 
gravel,  and  the  water  level  in  them  represented  the  ground-water  sur- 
face in  the  surrounding  soil.  An  average  of  the  observations  made  at 
a  given  time  was  assumed  to  represent  the  general  depth  to  ground- 
water for  the  tank  at  that  time.  The  tendency  of  the  sides  of  the  holes 
to  cave  in  and  the  bottom  to  fill  with  sand  was  controlled  by  casing 


253090 


184 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


SAFE   YIELD   OF   UNDEKGROUND   RESEEVOTRS  185 

them  with  2-in.  galvanized  sheet-iron  pipe  generously  perforated  with 
Y^(v-in.  holes.  These  pipes  were  driven  so  tha.t  the  top  was  just  flush 
with  the  ground  surface,  and  they  were  closed  at  the  top  with  wooden 
plugs.  In  some  of  the  tanks  it  was  found  impossible  to  bring  the 
ground-water  surface  to  the  desired  level  with  the  available  hydrostatic 
pressure  from  the  reservoir  tanks,  and  2-in.  holes  were  bored  between 
the  observation  holes  to  the  saturated  gravel  layer.  Water  usually 
rose  in  these  holes  to  the  same  height  as  in  the  reservoir  tank,  and,  by 
seeping  laterally  into  the  soil,  built  up  the  ground-water  surface.  It 
was  found  difficult  to  keep  these  holes  open  to  the  gravel,  however, 
and  the  water  level  in  most  of  them  eventually  represented  the  ground- 
water surface. 

Three  tank  sets  were  installed  in  the  open  valley  floor  east  of  Inde- 
pendence in  February,  1909.     The  surface  of  Soil  Tank  No.  1  was  bare  "' 
sand;  Nos.  2  and  3  (Fig.  7)  were  laid  with  salt-grass  sod.     The  initial               *    ^ 
plan  formulated  for  Tank  Sets  Nos.  1  and  3  was  to  hold  the  ground-             ^   (J 
water  level  at  various  depths  below  the  ground  surface  for  periods  of  a           "^   }^ 
few  weeks  during  the  summer  while  the  climatic  conditions  were  con-         *~    ^ 
stant,  in  order  to  obtain,  in  a  short  time  and  with  few  tanks,  trust-       ^    ^. 
worthy  results  of  a  general  nature.     The  movement  of  the  water  sur-     ft 
face  from  one  level  to  another  consumed  so  much  time,  however,  that 
winter   approached   before   the   experiments   on   the  lower  levels    were 
reached,  and  furthermore,  there  was  no  accurate  method  of  determin- 
ing the  volume  of  evaporated  water  represented  by  the  differences  in 
depth.      The    experience    of    the    first   year's    work    with    these    tanks 
showed  the  necessity  of  maintaining  a  fixed  ground-water  level  during 
a  complete  cycle  of  climatic  changes.     In  Soil  Tank  No.  2  it  was  at 
first  proposed  to  hold  the  ground-water  level  at  or  near  the  ground 
surface,  but  so  great  was  the  rate  of  summer  evaporation  that  this 
plan  was  found  to  be  impracticable  with  the  equipment  available.     To 
remedy  the  defect,  the  hydrostatic  pressure  from   the   reservoir  tank 
was  increased  by  soldering  to  it  a  3-ft.  extension,  but  this  was  not  used 
until  late  in  the  season.     This  experience  suggested  the   desirability 
of  placing  the  reservoir  tanks  above  the  soil  tanks  and  of  increasing 
the  size  of  the  feed  pipe. 

As  a  result  of  these  preliminary  observations,  four  additional  tank 
sets  were  installed  in  January,  1910.  The  reservoir  tank  outlets  were 
placed  about  1.7  ft.  above  the  soil  tank  inlets,  and  1-in.  pipe  was  used 


186 


SAFE    YIELD   OF   UNDERGROUND    RESERVOIRS 


throughout.  The  new  soil  tanks  were  laid  with  salt-grass  sod,  which 
took  root  and  grew  in  every  tank.  The  general  plan  of  operation  for 
Tank  Sets  Nos.  2  to  7  was  to  supply  the  reservoir  tanks  with  water  in 
quantities  such  that  the  depths  to  ground-water  in  the  soil  tanks  were, 
respectively,  5  ft.,  4.5  ft.,  4  ft.,  3  ft.,  2  ft.,  and  1  ft.  Observations  were 
carried  on  continuously  on  the  six  tanks  during  the  two  years,  1910 

INFLUENCE  OF  ALTITUDE  ON   EVAPORATION 
FROM  WATER  SURFACE  ON  THE  EASTERN 
SLOPE  OF  MOUWT  WHITNEY,  CALIFORNIA. 


14000 


13000 


«  10000 

P4 


S    8000 


6000 


4000 


n    *^ 

mmit,  Mt.Wliit 

ley,  Ele 

.  U502 

t. 

Observations  made  duiing-  the  summer 
of  1905  by  office  of  Experiment  Stations, 
U.S.  Dept.  At'iiculture. 
Water  contained  in  cylindrical  tank  22  in 
diani.,  28  in.  deep,  set  in  soil. 

r,    Me: 

icau  Ca 

mp,  Ele 

•.  12000 

ft. 

\ 

i\    Loi 

e  Pine  1 

^ake.  El 

!v.  10000 

ft. 

\ 

3 

V^unt 

rs  Cam 

1,  Elev. 

i370  ft. 

• 

"^ 

\2 

unction 

South  I 

ork  and 

Lone  P 

ne  Ciee 

i  Elev. 

:i25  ft. 

\ 

N 

\ 

N^Sold 

er-sCar 

ip,  Ele\ 

4515  ft 

20 


30  35  40  4J 

Daily  Evaporation,  in  Hundredths  of  an  inch. 


50 


Fig.  9. 
and  1911.     The  operation  and  results  were  quite  satisfactory,  with  the 
exception  that  in  Tank  Set  No.  7  the  pressure  from  the  reservoir  tank 
was   not   sufficient   between   April   and    September    to   hold   the   water 
level  at  the  1-ft.  depth. 

An  important  feature  of  reproducing  natural  conditions  for  com- 
bined soil  evaporation  and  transpiration  is  to  obtain  a  fully  developed 
root  system  reaching  down  to  the  ground-water  surface.     At  best,  this 


SAFE   YIELD   OF    UNDERGROUND   RESERVOIRS  187 

requires  more  than  a  year,  particularly  for  the  greater  depths.  In 
order  to  stimulate  the  growth  as  much  as  possible,  the  water  level  in 
all  soil  tanks  was  brought  up  to  about  1  ft.  below  the  surface  as  soon 
after  installation  as  possible.  This  was  accomplished  by  pouring  water 
into  the  observation  holes  until  the  soil  was  completely  saturated  to 
the  level  desired  and  the  surface  showed  moisture.  Then  no  water  was 
added  to  the  reservoir  tanks  until  the  ground-water  level  had  receded 
by  evaporation  and  transpiration  to  the  desired  level.  The  grass 
roots  were  thus  given  a  good  initial  irrigation  and  an  opportunity  to 
follow  the  water  down.  Active  growth  occurred  in  Tanks  Nos.  4  to  7 
during  the  first  year,  and  continued  with  greater  vigor  during  the  sec- 
ond year.  In  Tank  No.  3  a  less  active  growth  occurred  the  first  year, 
but  the  results  were  more  satisfactory  during  the  second  year.  There 
was  practically  no  growth  in  Tank  No.  2  during  the  first  year,  although 
the  grass  did  not  die.  During  the  second  year  the  grass  showed  more 
signs  of  life,  but  did  not  grow  as  actively  as  in  Tank  No.  3. 

The  details  of  the  observations  on  soil  evaporation  for  1910  and 
1911  for  Tank  Set  No.  5  are  shown  graphically  on  Plate  IV.  The  sup- 
ply of  water  available  to  the  soil  from  the  reservoir  tank  is  the  element 
under  complete  control  of  the  observer,  and  at  the  top  of  the  diagram 
are  statements  of  the  purpose  governing  additions  to  or  withdrawals 
from  this  supply  during  various  periods  of  time.  Below  this  is  platted 
a  broken  line  representing  the  fluctuation  of  water  surface  in  the  reser- 
voir tank,  the  vertical  portions  indicating  additions  to  or  withdrawals 
from  the  reservoir  supply  made  by  the  observer,  and  the  inclined  por- 
tions indicating  the  soil-tank  draft.  There  is  also  platted  a  mass-curve 
showing  the  aggregate  volume  of  water  supplied  to  the  reservoir  tank, 
which  appears  as  a  series  of  vertical  and  horizontal  lines.  At  the 
bottom  of  the  diagram  is  platted  an  undulating  line  representing  the 
fluctuation  of  ground-water  surface  in  the  soil  tank,  each  depth  being 
obtained  by  averaging  the  depths  recorded  in  the  observation  holes. 

The  small  part  that  precipitation  plays  in  ground-water  fluctuations 
in  Owens  Valley  is  shown  by  this  diagram.  The  average  annual  pre- 
cipitation at  the  experiment  station  is  about  4.38  in.,  the  season, 
1909-10,  being  normal  and  1910-11  well  above  normal.  At  the  bottom 
of  the  diagram  is  noted  the  date  and  quantity  of  precipitation  for  ea,ch 
storm.  It  is  seen  that,  even  in  a  wet  season,  percolating  water  does 
not  penetrate  to  depths  exceeding  2.5  ft.,  unless  more  than  1  in.  falls 


188 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


within  a  short  period  on  moist  soil.  Even  then  it  does  not  appear 
to  reach  depths  greater  than  4  ft.  The  problem  of  percolation  from 
rainfall,  therefore,  is  practically  eliminated  from  the  experiments. 
When  rising  ground-water  was  noted  in  a  soil  tank  after  precipitation, 
the  volume  of  percolating  water  was  estimated  from  the  observed  rise 
and  included  in  the  mass-curve,  as  noted  on  the  diagrams. 

The  quantity  of  water  evaporated  from  the  soil  surface  of  any 
tank  during  a  given  period  can  be  computed  accurately  from  the  dia- 
grams, when  the  depth  to  ground-water  at  the  beginning  and  end  of 
the  period  is  the  same,  by  noting  from  the  mass-curve  the  quantity 
supplied  to  the  reservoir  tank  during  the  period  and  the  accumulation 
or  depletion  in  the  reservoir  tank.  The  sum  of  these  quantities,  with 
their  proper  algebraic  sign,  gives  the  loss  by  evaporation.  For  differing 
depths  to  ground-water,  however,  the  computations  are  only  approxi- 
mate, because  the  proportion  of  empty  space  in  the  soil  layer  and  the 
quantity  of  moisture  it  contained  initially  are  both  unknown.  A 
monthly  summary  of  results  for  Tank  Sets  Nos.  2  to  7  for  1911  is 
presented  in  Tables  9  to  14.  The  annual  depth  of  evaporation  from 
the  several  soil  tanks  exhibited  a  consistent  decrease  with  increase 
of  depth  to  ground-water,  and  varied  from  48.8  in.  for  No.  7  to  13.43 

TABLE  9. — Depth  of  Evaporation  From  Ground  Surface  Near 

Independence  During  1911. 

Tank  Set  No.  2. 


Volume 
of  water 
supplied 

to 
reservoir 
tank,  in 
gallons. 

Depth  op  Water 

IN  Reservoir 

Tank,  in  Feet. 

Accumu- 
latiou  or 
depletion 
of  water 

in 

reservoir 

tank,  in 

gallons. 

Volume  of  Water 
Evaporated. 

Average 
depth  to 
ground- 
water 

Month. 

Begin- 
ning of 
month. 

End  of 
month. 

Total, 

in 
gallons. 

Depth, 

in 
inches. 

Rate,  iu 
inches 
per  24 
hours. 

surface 

in 

soil  tank, 

in  feet. 

Jan 

Feb 

Mar 

Apr 

May 

June  

July 

Aug: 

Sept 

Oct 

Nov 

Dec 

6 
0 
3 

10 

30 

(56 

71 

105 

53 

18 

1 

1 

1.10 
1.15 
1.11 
1.14 
1.18 
1.19 
1.39 
1.22 
1.78 
1.52 
1.37 
1.18 

1.15 
1.11 
1.14 
1.18 
1.19 
1.39 
1.22 
1.78 
1.53 
1.37 
1.18 
(1.10) 

+    2 

—  1 

+    1 

+    1 

0 

±^5 
+  18 

—  8 

—  5 

—  6 

—  3 

4 

1 

2 

9 

30 

60 

76 

87 

60 

23 

7 

4 

0.15 
0.04 
0.07 
0.33 
1.11 
2.23 
2.81 
3.22 
2.22 
0.85 
0.26 
0.15 

0.005 
0.001 
0.f)02 
0.011 
0.036 
0  074 
0.091 
0.104 
0.074 
0.028 
0.009 
0.005 

4.98 
4.95 
4.94 
4.94 
4.98 
5.03 
5.00 
4.95 
4.80 
4.80 
4.85 
4.98 

Year 

363 

1.10 

1.10 

0 

363 

13.43 

0.037 

4.94 

SAFE   YIELD   OF   UNDEKGROUND   RESERVOIRS 


189 


TABLE  10. — Depth  of  Evaporation  From  Ground  Surface  Near 
Independence  During  1911. 

Tank  Set  No.  3. 


Volume 
of  water 
supplied 
to  reser- 
voir 
tank,  in 
gallons. 

Depth  of  Water 
IN  Reservoir 
Tank,  in  Feet. 

Accumu- 
lation or 
ilepletion 
of  water 
in  reser- 
voir 
tank,  in 
gallons. 

Volume  op  Water 
Evaporated. 

Average 
depth   to 
ground- 
water 

Month. 

Begin- 
ning of 
month. 

End  of 
month. 

Total. 

in 
gallons. 

Depth, 

in 
inches. 

Rate,  in 
inches 
per  24 
hours. 

surface 

in  soil 

tank,  in 

feet. 

Jan 

Feb 

Mar 

Apr 

May 

June 

July 

Aug 

Sept 

Oct 

Nov 

Dec  

9 

IH 

12 

40 

62 

103 

160 

285 

135 

27 

4 

3 

n.i4 
1.10 
0.23 
0.20 
0.54 
0.60 
0.96 
0.67 
2.00 
1.13 
0.54 
0.16 

0.10 
0.23 
0.-.20 
0.54 
0.60 
0.98 
0.67 
2.00 
1.13 
0.54 
0.16 
(0.10) 

—  1 
+     4 

—  1 
+  11 
+    2 
+  12 

—  9 
-1-  43 

—  28 

—  19 

—  12 

—  2 

10 

14 

13 

29 

60 

91 

169 

242 

163 

46 

16 

5 

0.37 
0.52 
0.48 
1.07 
3.22 
3.37 
6.25 
8.S6 
6.03 
1.70 
0.59 
0.18 

0.012 
0.019 
0.015 
0.036 
0.072 
0.112 
0.202 
0.289 
0.201 
0.055 
0.020 
0.006 

4.53 
4.59 
4.48 
4.50 
4.49 
4.63 
4.51 
4.52 
4.22 
4.21 
4.33 
4.56 

Year 

858 

0.14 

0.10 

0 

8£8 

31.74 

0.087 

4.46 

TABLE  11. — Depth  of  Evaporation  From  Ground  Surface  Near 
Independence  During  1911. 

Tank  Set  No.  4. 


Month. 

Volume 
of  water 
supplied 
to  reser- 
voir 
tank  in 
gallons. 

Depth  of  Water 

IN  Reservoir 
Tank,  in  Feet. 

Accumu- 
lation or 
depletion 
of  water 
in  reser- 
voir 
tank,in 
gallons. 

Volume  of  Water 
Evaporated. 

Average 
depth  to 
ground- 
water 

Begin- 
ning of 
month. 

End  of 
month. 

Total, 

in 
gallons. 

Depth, 

in 
inches. 

Rate,  in 
inches 
per  24 
hours. 

surface 
in  soil 

tank,  in 
feet. 

Jan 

Feb 

Mar 

Apr 

May 

June 

July 

Aug 

Sept 

Oct 

Nov 

Dec 

7 

—  8 

3 

62 

96 

121 

114 

141 

65 

30 

9 

6 

1.53 
1.49 
1.18 
1.19 
2.15 
2.57 
2.63 
1.97 
2.47 
1.90 
1.53 
1.09 

1.49 
1.18 
1.19 
2.15 
2.57 
2.63 
1.97 
2.47 
1.90 
1.53 
1.09 
(0.91) 

—  1 

—  10 

0 
+  31 
+  14 
+    2 

—  21 
+  1-6 

—  18 

—  12 

—  14 

—  6 

8 

2 

3 

31 

82 

119 

135 

125 

83 

42 

23 

12 

0.30 
0.07 
0.11 
1.15 
3.04 
4.40 
5.00 
4.68 
3.07 
1.55 
0.85 
0.44 

0.010 

0.002 

0.004 

0.038 

0.098  ■ 

0.147 

0.161 

0.149 

0.102 

0.050 

0.028 

0.015 

3.97 
3  36 
3.74 
4.00 
4.06 
(3.34) 
3.44 
3,92 
3.85 
3.93 
3.97 
4.10 

Year 

646 

1.53 

0.91 

—  19 

665 

24.61 

0.067 

3.81 

o 

IT)      O 

o 


190 


SAFE    YIELD   OF   UNDERGROUND   RESERVOIRS 


TABLE  12. — Depth  of  Evaporation  From  Ground  Surface  Near 
Independence  During  1911, 

Tank  Set  No.  5. 


Month. 

Volume 
of  water 
supplied 
to  reser- 
voir 
tank,  in 
gallons. 

Depth  of  Water 
IN  Reservoir 
Tank,  in  Feet. 

Accumu- 
lation or 
depletion 
of  water 

in 
reservoir 
tank,  in 
gallons. 

Volume  op  Water 
Evaporated. 

Average 
depth  to 
ground- 
water 

Begin- 
ning of 
month. 

End 

of 

month. 

Total, 

in 
gallons. 

Depth, 

in 
inches. 

Rate,  in 
inches 
per  24 
hours. 

surface 

in  soil 

tank,  in 

feet. 

Jan 

Feb 

Mar 

Apr 

May 

June 

July 

Aug 

Sept 

Oct  

8 

6 

3 

88 

141 

166 

244 

255 

127 

36 

9 

1 

2.55 
2.43 
2.42 
2.. 36 
3.65 
4.09 
4.19 
4.14 
4.92 
4.07 
3.24 
2.67 

2.43 

2.42 
2. .36 
3.65 
4.09 
4.19 
4.14 
4.92 
4.07 
3.24 
3.67 
(2.45) 

—  4 

0 

—  2 

+  42 
4-  14 
-i-    3 

—  2 
+  23 

—  25 

—  27 

—  18 

—  7 

12 

6 

5 

46 

127 

163 

246 

232 

152 

63 

27 

8 

0.44 
0.22 
0.18 
1.70 
4.70 
6.03 
9.11 
8.58 
5.62 
2.33 
1.00 
0.30 

0.014 
0.008 
0.006 
0.057 
0.151 
0.201 
.     0.294 
0.280 
0.188 
0.075 
0.033 
0.010 

3.01 
2.47 
2.73 
2.99 
3.01 
3.40 
3.06 
2.99 
2.69 
2.77 

Nov 

Dec 

2.83 
2.90 

Year 

1084 

2.55 

2.45 

—    3 

1087 

40.21 

0.110 

2.90 

TABLE  13. — Depth  of  Evaporation  From  Ground  Surface  Near 
Independence  During  1911. 

Tank  Set  No.  6. 


Month. 

Volume 
of  water 
supplied 
to  reser- 
voir 
tank,  in 
gallons. 

Depth  of  Water 
IN  Reservoir 
Tank,  in  Feet. 

Accumu- 
lation or 
depletion 
of  water 
in  reser- 
voir 
tank,  in 
gallons. 

Volume  of  Water 
Evaporated. 

Average 
depth  to 
ground- 
water 

Begin- 
ning of 
month. 

End  of 
month. 

Total,  in 
gallons. 

Depth,  in 
inches. 

Rate,  in 
inches 
per  24 
hours. 

surface 

in  soil 

tank,  in 

feet. 

Jan 

Feb 

Mar 

Apr 

May 

June 

July 

Aug 

Sept 

Oct 

12 

9 

24 

94 

163 

182 

213 

314 

143 

38 

8 

6 

3.03 
3.19 
3.17 
3.32 
3.53 
3.54 
3.75 
3.31 
4.25 
3.89 
3.36 
2.98 

3.19 
3.17 
3.32 
3.. 53 
3.54 
3.75 
3.31 
4.25 
3.89 
3.36 
2.98 
(2.83) 

+  5 

—  1 

+  7 
0 
+  7 
—14 
+30 
—12 
—17 
—12 

—  5 

7 

10 

19 

87 

163 

175 

227 

284 

155 

55 

20 

11 

0.26 
0.37 
0.70 
3.22 
6.03 
6.48 
8.40 
10.50 
5.74 
2.04 
0.74 
0.41 

0.008 
0.013 
0.023 
0.107 
0.195 
0.216 
0.271 
0.8.39 
0.192 
0.065 
0.1  J25 
0.013 

1.92 
1.31 
1.70 
2.00 
1.99 
2.30 
2.02 
2.01 
1.55 
1.65 

Nov 

Dec 

1.84 
2.04 

Year 

1  206 

3.03 

2.83 

-  7 

1  213 

44.89 

0.122 

1.86 

SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


191 


TABLE  14. — Depth  of  Evaporation  From  Ground  Surface  Near 

Independence  During  1911. 

Tank  Set  No.  7. 


Month. 

Volume 
of  water 
supplied 
to  reser- 
voir 
tank,  in 
gallons. 

Depth  of  Water 

IN  Reservoir 

Tank,  in  Feet. 

Accumu- 
lation or 
depletion 
of  water 
in  reser- 
voir 
tank,  in 
gallons. 

Volume  of  Water 
Evaporated. 

Average 
depth  to 
ground- 
water 

Begin- 
ning of 
month. 

End  of 
month. 

Total, 

in 
gallons. 

Depth, 

in 
inches. 

Rate,  in 
inches 
per  24 
hours. 

surface 

in  soil 

tank,  in 

feet. 

Jan 

Feb 

Mar 

Apr 

May 

June 

July.- 

Aug 

Sept 

Oct 

Nov 

Dec 

3 

31 

67 

102 

151 

160 

223 

255 

178 

115 

14 

0 

5.07 
4.70 
5.08 
5.90 
5.96 
5.92 
5.62 
5.40 
5.99 
5.79 
5.77 
4.96 

4.70 
5.08 
5.90 
5.96 
5.92 
5.62 
5.40 
5.99 
5.79 
5.77 
4.96 
(4.50) 

—  12 
4-  12 
+  26 

+    2 

—  1 

—  10 

+  19 

—  6 

—  1 

—  26 

—  15 

15 
19 
41 

100 
1,52 
170 
230 
236 
184 
116 
40 
15 

n..n6 

0.70 
1.52 
S.70 
5.62 
6.30 
8.52 
8.74 
6.81 
4.29 
1.48 
0.56 

0.018 
0.025 
0.049 
0.123 
0.181 
0.210 
0.275 
0.281 
0.227 
0.139 
0.049 
0.018 

0.73 
0.81 
0.98 
1.46 
1.64 
2.06 
2.19 
2.51 
2.39 
1.44 
0.60 
0.60 

Year 

1  299 

5.07 

4.50 

—  18 

1  318 

48.80 

0.133 

1.45 

in.  for  No.  2.  The  depth  of  summer  evaporation  varied  from  81  to  90% 
of  the  annual  in  the  several  tanks,  and  averaged  87  per  cent.  The 
month  of  maximum  evaporation  is  August,  and  minimum  evaporation 
occurs  during  December  to  March,  inclusive.  The  exact  date  of  maxi- 
mum evaporation  rates  for  the  several  soil  tanks  occurs  about  Sep- 
tember 1st,  and  they  follow  each  other  consecutively  with  greater 
depth  to  ground-water.  The  approximate  dates  of  maximum  and 
minimum  air  temperatures  a.t  Independence  are  July  10th  and  Jan- 
uary 10th,  respectively,  but  no  measurements  were  made  to  determine 
the  lag  of  corresponding  soil  temperatures  at  various  depths.  The 
extremes  of  evaporation  from  water  surfaces  agree  in  time  of  occur- 
rence with  maximum  and  minimum  air  temperatures,  however,  and 
the  observed  lag  in  soil  evaporation  is  in  general  consistent  with  the 
observed  lag  in  soil  temperatures  in  other  localities.  Hence  it  is 
reasonable  to  conclude  that  extremes  in  the  rate  of  soil  evaporation 
and  soil  temperature  are  concurrent  at  a  given  depth. 

A  graphic  study  of  the  data  in  Tables  9  and  14  for  the  periods, 
April  1st  to  September  30th,  and  October  1st  to  March  31st,  which 
are,  respectively,  periods  of  increasing  and  decreasing  evaporation 
rate,  is  presented  in  Fig.  10.     There  appears  to  be,  during  each  period, 


193 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


a  straight-line  relation  between  total  evaporation  and  depth  to  ground- 
water. The  limiting  depth  is  7,7  ft.,  and  the  total  evaporation  when 
water  and  ground  surface  coincide,  54.0  and  8.2  in.,  respectively.  The 
total  depth  of  evaporation,  in  inches,  being  represented  by  E,  and 
the  depth  to  ground-water,  in  feet,  by  D,  the  equations  representing 
variation  in  evaporation  with  depth  to  ground-water  are  E  =  54.0  — 
7.00  D  and  E  =  S.2  —  1.17  D.  It  will  be  noted  that  the  combined 
soil  evaporation  and  transpiration  during  the  summer  exceeded  the 
water  evaporation  from  the  tanks  in  the  soil  by  15  per  cent. 


OWENS  VALLEY  SOIL  EVAPORATION  CURVES 

FOR  ALKALI  SALT  GRASS  LAND 

Based  on  Soil  Tank  Observations  of  1911. 

Curve  based  on  I'JII  Data. 

Curve  based  on  11)10-11  Data. 

O      I'.ill  Observations. 

Fig.  10. 

The  curve  based  on  the  1910-11  data  is  shown  on  the  diagram 
for  comparison.  There  was  a  marked  increase  in  total  evaporation 
during  1911,  as  compared  with  the  season,  1910-11,  which  was  due  to 
the  more  complete  development  of  the  root  systems.  Broadly  speaking, 
the  results  for  1911  showed  an  increase  of  17%  in  the  volume  of  water 
consumed  during  the  two  periods.  A  continuation  of  observations  for 
another  year  would  show  still  further  increase  for  those  tanks  in 
which  the  grass  roots  had  not  reached  the  water  plane.  Observations 
of  depth  to  water  in  test  holes  in  the  transition  zone  between  meadow 
and  desert  land  indicate  that  soil  evaporation  ceases  for  depths  ex- 
ceeding 8  ft.  The  effect  of  increased  evaporation  for  the  tanks  with 
greatest  depth  to  ground-water  would  be  to  drop  the  lower  end  of  the 


SAFE    YIELD   OF   UNDERGROUND   RESERVOIRS  193 

curve  to  some  point  below  7.7  ft.  The  true  curve,  therefore,  is  prob- 
ably steeper  than  that  for  1911,  crossing  the  X-axis  at  about  the  same 
point,  but  the  I'-axis  at  about  8  ft.  instead  of  7.7  ft.  However,  in  the 
practical  use  of  the  curve,  the  departure  of  the  lower  end  from  the 
true  position  does  not  affect  materially  the  computations  of  the  total 
volume  of  water  evaporating  from  a  given  area,  as  the  proportion  of 
such  volume  originating  in  areas  of  relatively  deep  ground-water  is 
small. 

Transpiration. — A  considerable  portion  of  the  water  evaporating 
from  the  soil  is  absorbed  by  plant  roots  and  carried  upward  through  the 
stem  and  into  the  foliage,  whence  it  escapes  in  the  process  of  trans- 
piration. This  process  continues  as  long  as  the  plant  has  life,  but  is 
most  active  during  the  growing  period.  Transpiration  differs  in  differ- 
ent species  of  plants,  and  even  in  the  same  species  when  existing 
under  different  conditions  of  light,  atmospheric  pressure,  soil  texture, 
and  available  moisture  in  the  soil.  King's  experiments  indicate  that 
humidity  does  not  affect  transpiration.*  For  a  species  growing  in  a 
definite  locality,  light  and  available  soil  moisture  are  the  controlling 
factors. 

The  process  of  transpiration  and  respiration  in  plants  is  similar 
to  the  breathing  of  animals.  Both  plants  and  animals  inhale  air  and 
exhale  from  the  respiratory  organs  large  quantities  of  water.  The 
lungs  of  animals  are  intended  primarily  to  provide  a  means  for  the 
entrance  of  oxygen  into  the  body  and  for  the  escape  of  carbon  dioxide, 
but  they  cannot  perform  their  functions  unless  the  interior  lining  of 
the  air  cells  is  kept  moist.  Similarly,  the  breathing  surface  of  a  plant 
must  be  kept  moist,  and,  as  a  protection  from  too  rapid  evaporation, 
this  surface  is  within  the  plant  structure,  principally  in  the  foliage. 
Plant  leaves  are  enclosed  in  a  relatively  impervious  skin  or  epidermis 
in  which  are  small  breathing  pores  or  stomata  which  open  or  close 
automatically,  depending  on  the  needs  of  the  plant  for  a  greater  or  less 
quantity  of  air.  When  exposed  to  light,  the  food-manufacturing  proc- 
esses of  a  green  plant  are  stimulated,  and  require  a  continually  chang- 
ing volume  of  air  in  contact  with  the  breathing  surface.  The  stomata 
open  proportionally  to  the  light  intensity.  Should  the  water  supply 
in  contact  with  the  roots  be  insufficient,  the  breathing  surface  may  be- 
come dry,   and  when   that  happens   the   stomata   close   automatically 

*  ''  Irrigation  and  Drainage,"  by  F.  H.  King,  New  York,  1899. 


194 


SAFE   YIELD   OF    UNDERGROUXD   RESERVOIRS 


until  the  proper  quantity  of  air  is  admitted  for  the  plant  to  do  its 
work  under  the  new  conditions.  The  stomata,  therefore,  control  the 
quantity  and  rate  of  loss  of  water  from  plants  by  transpiration. 

There  is  a  marked  diurnal  periodicity  in  the  rate  of  transpiration, 
which  investigators  are  led  to  believe  is  largely  the  result  of  the 
varying  intensity  of  light.     This  periodicity  is  well  illustrated  by  ob- 


6  P.M.  8       10    12  Mt.2        4        (i        8       10      12  M.  2        -t      6  P.M. 

RELATION  OF  TRANSPIRATION  TO   LIGHT  INTENSITY 
DURING  A  24-HOUR   DAY. 
Fig.  11. 

servations  made  under  the  direction  of  Mr.  Frederick  E.  Clements, 
State  Botanist  of  Minnesota,  and  reproduced  in  Fig.  11.*  Measure- 
ments of  transpiration  were  made  hourly  from  6  p.  m.  on  February 
16th  to  6  p.  M.  on  February  17th,  and  the  physical  factors  were  ob- 
served between  these  hours.     The  day  was  cloudy  throughout,  so  that 

♦"Influence  of  Physical  Factors  on  Transpiration",   by  A.  W.  Sampson  and  L.  M. 
Allen,  Minnesota  Bot.  Studies,  Pt.  I,  Vol.  4,  1909,  p.  42. 


SAFE    YIELD   OF    UXDERGROUXD    RESERVOIRS 


195 


the  variation  in  temperature  and  humidity  was  slight.  The  diagrams 
show  very  strikingly  the  response  of  transpiration  to  changes  in  in- 
tensity of  light. 

No  measurements  of  transpiration  are  available  for  conditions  simi- 
lar as  regards  altitude  and  aridity  to  those  in  Owens  Valley.  It  is  un- 
necessary in  this  study  to  l^now  separately  the  transpiration  from  wild 
grasses  and  the  evaporation  from  bare  soil,  because  the  area  of  the 
latter  is  relatively  small.  The  experiments  on  soil  evaporation,  there- 
fore, were  planned  to  give  the  combined  loss  from  these  two  causes.  It 
is  desirable,  however,  to  know  the  quantity  of  transpiration  from  field 
crops,  in  order  to  aid  in  computing  the  quantity  of  percolation  from 
irrigation.    Observations  for  such  crops  were  confined  to  alfalfa. 


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Notes.-  Samples  cut  Aug.  9th,  1910.  near  Independ- 
ence. Alfalfa  in  full  bloom,  standing  34  to 
30  in.  high,  and  normally  developed. 
Each  sample  covered  Isq.  yd.  standing, 
and  was  spread  on  paper  so  as  to  cover  the 
same  area  when  drying.  Wilting  noticeable 
at  end  of  13  min.  Total  loss  of  raoist- 

r^ 

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RATE  OF  LOSS  OF  WATER  FROM  FRESHLY  CUT  ALFALFA,  BASED  ON  FIELD  AREAS. 

FIG.   12. 

The  method  of  measurement  was  based  on  the  assumption  that  the 
rate  of  loss  of  water  from  freshly  cut  plants  would  correspond  closely 
to  the  rate  before  cutting.  The  plants  were  cut  rapidly  from  a  meas- 
ured area,  weighed,  and  spread  out  on  paper  to  cover  the  same  area 
as  before  cutting.  At  short  intervals  they  were  reweighed  until  there 
was  no  further  appreciable  loss.  No  noticeable  wilting  occurred  dur- 
ing the  first  15  min,  and  the  rate  of  loss  during  this  period  was  used  as 


196  SAFE    YIELD   OF   UNDERGROUND   RESERVOIRS 

a  basis  for  calculations.     The  results  of  the  measurements  are  shown 
graphically  in  Fig.  12. 

The  rapid  decrease  in  the  rate  of  loss  is  very  noticeable.  Inspec- 
tion of  Fig.  11  will  show  that  the  rates  of  transpiration  at  8.45,  9.15, 
and  10.30  a.  m.,  and  2.02  p.  m.^  expressed  as  percentages  of  the  aver- 
age rate  for  24  hours,  are,  respectively,  128,  141,  177,  and  197,  an  aver- 
age of  161  per  cent.  If  a  similar  relation  is  assumed,  the  average  loss  in 
a  24-hour  day  from  the  four  alfalfa  samples  would  be  366  oz.  per  sq.  yd. 
of  field  area,  or  0.49  in.  in  depth.  This  figure  appears  to  be  rather  large, 
at  first  glance,  for  the  rate  of  evaporation  for  that  day  from  the  pan  in 
Owens  Kiver  was  0.30  in.,  and  that  from  the  shallow  pan  in  the  soil 
was  0.38  in.  The  results  obtained  by  German  investigators  indicate  the 
loss  from  sod  during  the  growing  season  to  be  92%  greater  than  from 
water  surface,  and  that  from  cereals  to  be  73%  greater.  Furthermore, 
the  humidity  of  the  air  after  passing  over  an  alfalfa  field  is  very 
noticeably  greater  than  after  crossing  a  body  of  water.  The  result  ob- 
tained in  the  experiment  here  described,  therefore,  is  within  reason. 

The  growing  season  for  alfalfa  in  the  vicinity  of  Independence  is 
marked  by  an  entire  absence  of  cloudiness.  It  extends  from  about  April 
15th  to  September  30th,  during  which  time  three  crops  mature,  the 
yield  being  about  5  tons  of  drj-  matter  to  the  acre.  The  samples  used 
for  the  experiments  were  almost  ready  for  the  second  cutting.  On  the 
assumption  that  the  average  area  of  transpiring  surface  during  the 
entire  growing  season  was  50%  of  that  on  the  day  of  the  experiment, 
the  total  loss  of  water  during  the  season  would  amount  to  41  in.,  or 
3,43  ft.  in  depth.  Therefore,  with  a  production  of  dry  hay,  amounting 
to  5  tons  to  the  acre,  there  would  be  1  lb.  of  dry  matter  for  every  935 
lb.  of  water  lost  by  transpiration. 

Ground-Water. 

Form  of  the  Ground-Water  Surface.— The  general  form  of  the 
ground-water  surface  corresponds  with  that  of  the  surface  of  the  val- 
ley fill,  although  the  slopes  are  less  steep  and  the  irregularities  are  not 
so  pronounced.  In  the  valley  floor  the  depth  to  ground-water  is  only  a 
few  feet.  It  becomes  progressively  greater  toward  the  mountains,  and 
probably  lies  200  or  300  ft.  beneath  the  outwash  slope  at  about  the  5  000- 
ft.  contour.  Superimposed  on  the  general  ground-water  surface  are 
sharp  "ridges"  beneath  stream  channels  and  "mounds"  under  irrigated 


SAFE    YIELD   OF    rXDERGEOUX])    RFSEHVOIKS  197 

fields.     The  surface  of  the  water  in  the  underground  reservoir,  there- 
fore, is  not  a  level  plain,  but  has  a  varied  topography. 

There  are  two  reasons  for  this  condition :  the  action  of  gravity 
tending  to  equalize  inequalities  in  the  ground-water  surface,  and  the 
resistance  which  the  ground  offers  to  the  lateral  motion  of  water  through 
its  interstices.  Percolating  waters  enter  the  valley  fill  from  the  upper 
edge  of  the  outwash  slope,  from  stream  channels  crossing  the  outwash 
slope,  and  from  irrigated  fields.  The  valley  floor  is  the  lowest  portion 
of  the  valley  fill  and  also  the  ground-water  outlet.  The  force  of  gravity, 
therefore,  tends  to  draw  percolating  water  which  has  reached  the  sur- 
face saturation  to  the  level  of  the  valley  floor.  This  can  occur  only 
by  a  lateral  movement  of  water  from  the  outwash  slope  toward  the 
valley  floor,  but  the  resistance  of  the  porous  material  is  so  great  that  a 
steep  gradient  is  necessary  to  maintain  even  a  very  low  velocity.  Hence 
there  is  the  steep  slope  of  the  ground-water  surface  from  the  mountains 
toward  the  valley,  at  many  points  exceeding  80  ft.  per  mile,  and  laterally 
from  stream  channels  and  irrigated  fields.  The  lateral  movement  of 
the  water  is  so  slow  that  percolating  water,  entering  at  the  upper  edge 
of  the  outwash  slopes,  does  not  reach  the  valley  for  at  least  2  years. 

In  order  to  outline  the  ground-water  definitely,  all  existing  domestic 
wells  in  the  region  were  located  and  many  additional  observation  wells 
were  drilled,  where  the  cost  was  not  prohibitive.  The  region  contains 
27  domestic  wells,  12  of  which  are  on  the  valley  floor  and  15  on  the 
outwash  slopes.  There  were  drilled  in  addition  142  observation  wells, 
all  but  two  being  on  the  valley  floor.  These  wells  were  sufficient  to  de- 
fine the  ground-water  surface  over  about  60  sq.  miles  of  the  region. 

Ground-water  contours  for  the  valley  floor  showing  lines  of  equal 
average  depth  to  ground-water  have  been  worked  out  on  Plate  V.  They 
represent  the  average  position  of  the  surface  of  saturation  between  the 
annual  extremes.  The  data  are  sufficient  to  determine  the  3-,  4-,  and 
8-ft.  contours  with  reasonable  accuracy.  The  sudden  approach  of  ground- 
water toward  the  surface  at  the  upper  edge  of  the  grass  land  is  shown, 
and  also  the  general  proximity  of  ground-water  to  the  surface  through- 
out the  valley  floor.  The  total  area  between  the  westerly  8-ft.  contour 
and  Owens  Eiver  is  67  sq.  miles.  The  average  depth  to  ground-water 
is  between  4  and  8  ft.  over  40%  of  this  area,  and  between  3  and  4  ft. 
over  28  per  cent.  It  exceeds  8  ft.  over  14%  of  the  area,  and  is  3  ft. 
or  less  over  18  per  cent.     The  area  of  the  valley  floor  is  66.4  sq.  miles 


198  SAFE   YIELD   OF   UNDEKGROUND   RESEEVOIRS 

(Table  1),  and  its  west  boundary  practically  coincides  with  the  8-ft. 
contour. 

There  is  a  very  striking  relation  between  vegetation  and  depth  to 
ground-water.  On  the  outwash  slopes  the  vegetation  consists  of  vari- 
ous stunted  desert  shrubs.  In  approaching  the  valley  floor  at  about  the 
20-ft.  contour,  sagebrush  begins  to  predominate,  and  has  a  luxuriant 
growth  as  far  east  as  the  12-ft.  contour,  where  it  is  replaced  by  grease- 
wood,  rabbit  brush,  and  coarse  bunch  grass.  In  the  vicinity  of  the 
8-ft.  contour,  salt  grass  begins  to  appear,  and  farther  east,  near  and 
within  the  area  inclosed  by  the  4-ft.  contour,  it  grows  luxuriantly. 
Within  the  3-ft.  contour,  fresh-water  grasses  thrive  where  there  is 
sufficient  surface  water  to  leach  out  and  carry  away  most  of  the 
alkali,  but  the  salt  grass  grows  well,  even  where  the  soil  is  alkaline. 
In  various  portions  of  the  valley  floor  rabbit  brush  and  grease- 
wood  are  found  where  the  average  depth  to  ground-water  is  4  ft.  or 
more,  but  grass  predominates  east  of  the  8-ft.  contour.  In  areas  where 
the  alkali  is  excessive  there  is  practically  no  vegetation.  In  general, 
grass  does  not  grow  where  the  depth  to  ground-water  exceeds  8  ft., 
so  the  8-ft.  contour  tends  to  coincide  with  the  boundaries  between 
meadow  and  desert  lands. 

Fluctuation  of  the  Ground-Water  Surface.— The  surface  of  the 
ground-water  is  continually  fluctuating.  Both  the  extent  and  charac- 
ter of  this  fluctuation  vary  widely  in  different  localities  and  at  differ- 
ent times,  depending  on  the  proximity  to  ground-water  sources  or  out- 
lets and  the  relative  rates  of  ground-water  accretion  and  depletion. 
Three  pronoimced  types  are  to  be  observed  in  the  Independence  Basin : 
(1)  broad  irregular  fluctuations  of  varying  amplitude  in  the  outwash- 
slope  area;  (2)  slightly  irregular  periodic  fluctuation  with  wide  fixed 
limits  in  and  near  irrigated  areas;  and  (3)  a  regular  periodic  fluctua- 
tion with  comparatively  narrow  and  fixed  limits  in  the  valley  floor. 
Special  characteristics  are  also  exhibited  by  wells  within  certain  lim- 
ited areas,  as  the  result  of  local  ground-water  conditions. 

These  fluctuations  were  determined  and  studied  from  well  observa- 
tions made  by  the  methods  already  described.  Headings  obtained  at 
intervals  of  from  2  to  4  weeks  were  sufficient  to  establish  accurately 
the  position  of  the  ground-water  surface,  as  the  fluctuations  are  charac- 
terized by  great  regularity.  Most  of  the  wells  were  observed  from 
August  15th,  1908,  to  November  15th,  1909,  and  on  26  of  the  most 


PLATE  V. 

TRANS.   AM.  SOC.  CIV.  ENGRS, 

VOL.  LXXVIII,  No.  1315. 

LEE   ON 

YIELD  OF  UNDERGROUND  RESERVOIRS. 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  199 

typical  wells  observations  were  continued  to  May  1st,  1911.  The  fluc- 
tuation of  the  surface  of  the  lake  south  of  Citrus  Bridge  was  observed 
from  August  15th,  1908,  to  November  15th,  1909,  and  of  Goose  Lake 
from  August  15th,  1908,  to  May  1st,  1911. 

The  type  of  fluctuation  peculiar  to  wells  on  the  outwash  slope  is 
shown  on  Plate  VI  by  Wells  Nos.  31,  64,  25,  26,  and  59,  and  Citrus 
No.  1.  Water  stands  10  ft.  or  more  below  the  surface  in  all  these 
wells,  the  vegetation  of  the  surrounding  area  is  limited  to  desert  shrubs, 
and  there  are  no  alkali  deposits  on  the  surface.  With  knowledge  of 
the  sources  and  movements  of  ground-water  beneath  the  outwash  slopes, 
the  assigned  cause  for  this  type  would  be  annual  variation  in  the  quan- 
tity of  water  supplied  by  percolation  from  precipitation  on  the  inter- 
mediate and  outwash  slopes  and  from  stream  channels.  This  is  con- 
firmed by  the  observations.  For  example.  Well  No.  31,  which  is  7 
miles  from  the  base  of  the  Sierra  and  500  ft.  south  of  the  old  channel 
of  Pinyon  Creek,  exhibits  a  persistent  downward  tendency  which  was 
partly  checked  during  the  summer  of  1909  and  1910.  The  maximum 
effect  of  the  very  wet  years,  1906  and  1907,  evidently  reached  this  well 
in  1908  and  early  in  1909.  During  the  following  years  the  water  had 
a  tendency  to  return  to  its  normal  level.  This  was  twice  opposed  by 
percolation  from  the  channel  of  Pinyon  Creek,  which  carried  flood- 
water  during  a  few  weeks  in  June  and  July,  1909,  and  for  a  very  short 
period  in  1910.  Citrus  Well  No.  1,  which  is  about  |  mile  south  of 
Well  No.  31,  has  similar  fluctuations,  but  in  it  the  maximum  effect  of 
seepage  from  Pinyon  Creek  is  registered  6  weeks  later  in  1909,  and  in 
1910  is  much  smaller  in  quantity.  Well  No.  64,  situated  similarly 
with  respect  to  the  mountains,  but  north  of  Little  Pine  Creek,  has  the 
same  downward  tendency,  which  is  checked  temporarily  during  the  sum- 
mer by  irrigation  in  a  near-by  alfalfa  field  and  a  small  garden  at  the 
well.  Well  No.  59,  which  is  2  miles  from  the  base  of  the  Sierra  and 
i  mile  south  of  Sawmill  Creek,  had  an  upward  tendency  during  1909, 
due  to  the  percolation  from  precipitation  of  the  wet  winter,  1908-09. 
In  1910  the  water  level  fell  in  response  to  the  normal  winter  of  1909-10. 
Seepage  from  Sawmill  Creek  does  not  affect  this  well  appreciably. 
Wells  Nos.  25  and  26  exhibit  the  general  tendencies  of  Well  No.  59, 
but  they  are  in  the  transition  zone  between  the  outwash  slope  and  the 
valley  floor,  where  there  is  a  periodic  back-water  effect  from  the  annual 
rise  of  ground-water  in  the  grass  land. 


200  .        SAFE   YIELD   OF   UNDERGEOUXD   RESERVOIRS 

Wells  Nos.  61  and  62  illustrate  the  type  of  fluctuation  characteris- 
tic of  the  irrigated  areas  of  the  region.  They  are  in  irrigated  gardens 
in  the  Town  of  Independence.  The  form  of  the  curve  is  periodic,  with 
sharp  crests  and  troughs,  the  former  in  July,  the  latter  in  January  or 
February.  The  fluctuation  in  such  wells  ranges  from  10  to  20  ft.  in 
different  portions  of  the  basin.  Irregularities  superimposed  on  the 
broad  periodic  curve  are  the  result  of  irregularity  in  the  application 
of  irrigation  water. 

The  fluctuation  of  the  ground-water  surface  in  various  parts  of  the 
valley  floor,  other  than  at  the  eight  wells  already  mentioned,  is  shown 
by  48  typical  well  records  on  Plate  VI. 

Permanent  bench-marks  were  established  at  each  well,  and  test 
holes  from  which  measurements  to  the  water  surface  could  easily  be 
made  with  a  steel  tape.  Before  observing,  a  weight  is  fastened  at  the 
end  and  the  tape  is  chalked.  The  end  of  the  tape  is  then  submerged 
and  the  difference  between  the  readings  at  the  bench  and  at  the  water 
surface  is  the  depth.  Corrections  are  made  in  the  office  when  the  bench 
is  not  at  the  ground  surface.     Readings  are  to  feet  and  hundredths. 

Most  of  these  wells  are  where  the  average  depth  to  ground-water  is 
less  than  8  ft.  The  adjoining  ground  surface  is  more  or  less  crusted 
with  alkali,  and,  where  the  alkali  is  not  too  concentrated,  several  spe- 
cies of  wild  grass  grow  vigorously.  The  two  lakes  and  Wells  Nos.  C-3 
and  43  are  in  areas  where  the  average  depth  to  ground-water  exceeds 
8  ft.,  and  desert  conditions  prevail. 

The  fluctuations  observed  in  all  the  valley-floor  wells  are  remarkably 
uniform.  When  platted,  the  observations  give  smooth  and  regular 
curves  with  an  annual  periodicity.  The  average  time  of  occurrence 
of  crests  for  wells  in  grass  or  alkali  areas  is  March  28th;  the  troughs 
occur  on  September  20th,  6  months  later.  Heavy  winter  precipitation, 
or  the  proximity  of  springs,  advances  the  crests  into  January  or  Feb- 
ruary, but,  in  the  desert  areas,  the  crest  lags  into  April  or  May.  The 
fluctuation  between  maximum  and  minimum  levels  in  normally  situ- 
ated wells  ranges  from  1.5  to  4  ft.  Wells  which  are  near  or  below 
springs  in  the  vicinity  of  intermittently  occurring  surface  water  have 
a  greater  range,  which  may  reach  7  ft.  The  average  fluctuation  for 
1908-09,  as  observed  in  122  wells  distributed  generally  over  the  valley 
tloor,  is  3.14  ft.     This  average  represents  normal  conditions. 


E.TYPICAU 

.s 

N 

PLATE  VI. 
TRANS.  AM.  SCO,  CIV 
VOL.  LXXVIII,  No. 
LEE  ON 
YIELD  OF  UNDERGROUND 

ENGRS. 

1315. 

RESERVOI 

RS 

i 

i.|  Feb  1  MaijApr.iMaj  |Junej|Aui;.|Sept.|  Oct.  |No».lDeo.  J»n.  1  FebjMar.l  Apr.l  M«T|June|J.ul,l  Aug.|8ept.|  Oct.  I  Nov.  |  Dee.  J»d.|  Feb.|  .MarJ  Apr. 

19                                                                                   1910.                                                     1911. 
.  SECTION.               ELLS  IN  VICINITY  OF  S  SECTION. 

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SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  201 

Fluctuation  of  this  type  is  due  to  evaporation  from  the  soil  and 
transpiration,  processes  which  are  active  wherever  there  is  capillary 
connection  between  the  surface  of  saturation  and  the  ground  surface, 
or  wherever  gravity  water  or  capillary  water  is  within  reach  of  plant 
roots.  Two  facts  have  led  to  this  conclusion:  (1)  the  area  characterized 
by  capillary  connection  between  ground-water  surface  and  ground  sur- 
face and  by  accessibility  of  ground-water  to  plant  roots  is  coincident 
with  the  area  exhibiting  this  type  of  periodic  fluctuation;  and  (2)  the 
combined  rates  of  evaporation  from  soil  and  transpiration,  as  observed 
experimentally,  increase  and  decrease  concurrently  and  in  the  same 
ratio  with  the  fall  and  rise  of  the  ground-water  surface. 

The  first  of  these  facts  is  indicated  by  the  following  observations: 
Surface  incrustations  of  alkali  are  now  known  among  investigators  to 
be  an  indication  of  evaporation  from  the  soil,  and  a  growth  of  natural 
grasses  certainly  shows  the  presence  of  water  within  reach  of  plant 
roots.  These  manifestations  are  both  strictly  confined  to  valley-floor 
areas  within  which  the  periodic  fluctuation  is  observed.  There  are  val- 
ley-floor areas,  however,  within  which  the  periodic  fluctuation  occurs, 
but  which  have  a  loose  sandy  surface  devoid  of  alkali  and  vegetation. 
An  examination  of  such  areas  shows  that  they  are  surrounded  or  bor- 
dered by  meadow  and  alkali-crusted  land,  and  further  that  maximum 
and  minimum  ground-water  levels  exhibit  a  lag  in  time  of  occurrence 
which  varies  with  the  distance  from  these  adjoining  lands.  (See  Plate 
VI,  Well  C-3  and  Goose  Lake.)  The  fluctuations  in  these  desert 
areas  do  not  originate  within  the  areas  themselves  but  in  the  near-by 
lands,  from  which  they  are  propagated  as  annual  waves.  In  general, 
average  depths  to  ground-water  exceed  8  ft.  in  desert  areas  but  are  less 
than  8  ft.  in  meadow  or  alkali  lands. 

The  second  fact — that  variations  of  soil  evaporation  and  transpira- 
tion are  similar  to  ground-water  fluctuations — is  indicated  by  the  re- 
sults of  the  experiments  on  evaporation  from  soil.  The  maximum  rate 
of  soil  evaporation  occurs  about  September  1st  and  the  minimum  from 
December  1st  to  April  1st.  The  lowest  ground-water  level  occurs  about 
September  20th  and  the  highest  level  on  March  2Sth  (Plate  VII). 
Thus  the  critical  points  in  the  curves  of  soil  evaporation  and  ground- 
water fluctuation  are  practically  coincident  as  regards  time.  Further- 
more, although  the  curves  are  inversely  related,  their  form  is  remark- 
ably similar.    The  obvious  conclusion  is  that  ground-water  fluctuations 


202  SAFE   YIELD   OF   UXDERGROUND   RESERVOIRS 

in  non-irrigated  portions  of  the  valley  fill  are  the  result  of  evaporation 
from  the  soil  and  transpiration. 

Variations  from  the  normal  periodic  curves  occur  for  three  causes : 
large  precipitation,  seepage  from  springs,  and  seepage  from  standing 
or  flowing  surface  water.  The  infrequency  of  precipitation  sufficient 
to  raise  the  ground-water  surface  is  shown  on  Plates  VI  and  VII. 
It  is  practically  a  negligible  factor  in  ground-water  fluctuations. 
The  springs  at  the  upper  edge  of  the  outwash  slope  affect  ground-water 
conditions  in  their  vicinity  by  stimulating  the  annual  rise. and  main- 
taining the  ground-water  level  at  a  maximum  during  several  months 
prior  to  March.  (See  Plate  VI,  Wells  Nos.  46,  U-6A,  and  1-4.)  This 
results  from  the  decrease  in  the  rate  of  soil  evaporation  which  allows 
the  accumulation  of  their  discharge  in  the  surrounding  soil  at  a 
greater  rate  than  in  adjoining  areas  where  the  rate  of  supply  of  under- 
ground water  is  less.  Surface  water  has  its  source  in  large  springs, 
waste  from  irrigation,  and  the  flood  waters  of  mountain  streams.  It 
occurs  at  various  times  and  places,  and  cannot  be  considered  as  a  per- 
manent factor  in  ground-water  fluctuations.  (See  Plate  VI,  WelLs 
Nos.  4,  38,  39-A,  32,  and  GL-1.)  The  irregular  fluctuations  of  ground- 
water on  the  outwash  slope  do  not  appear  in  the  valley  floor  because 
of  the  relief  afforded  by  the  escape  of  water  in  springs  at  the  upper 
edge  of  the  grass  land. 

G7-ound-Water  Losses. — Ground-water  fluctuations  within  the  valley 
floor  consist  primarily  of  the  regular  annual  rise  and  fall  produced 
by  variation  in  the  rate  of  evaporation.  This  is  indicated  by  actual 
observations  extending  over  3  years,  and  confirmed  by  the  persistency 
of  various  perennial  plant  species.  Hence  there  must  be  overflow  of 
ground-water  from  the  valley  fill  of  the  region  equal  to  the  average 
inflow  by  percolation.  The  possible  outlets  would  seem  to  be  under- 
flow southward  through  the  valley  fill,  underflow  by  way  of  deep 
fissures,  seepage  and  spring  flow  into  the  channel  of  Owens  River, 
evaporation  from  spring  waters,  evaporation  from  damp  soil,  and 
transpiration  from  vegetation.  The  flrst  two  of  these  are  eliminated 
by  the  geology  and  topography  of  the  region.  The  slope  of  the  ground- 
water surface  in  the  valley  fill  opposite  the  Alabama  Hills  does  not 
exceed  8  ft.  to  the  mile,  and  the  material  is  fine  sand  and  clay,  as  in- 
dicated by  the  Southern  Pacific  Company's  well  at  Lone  Pine  Station. 
Even   if  there   is   a   movement   of   ground-water   southward   from   the 


PLATE   VII. 

TRANS.  AM.  SOC.  CIV.  ENGRS. 

VOL.  LXXVMI,  No.  1315. 

LEE    ON 

YIELD  OF  UNDERGROUND  RESERVOIRS. 


flucthdence. 


I  Aug.  I  Sept.l  Oct.  I  XoT.  I  Deo,  j  Jon.  |  Feb.  |  M»r.  I  Apr.TM^7-[A^  May  I  June  I  July  I  Aug.|  Sept.  I  Pot.  I  No».  I  Dec. 

1908 1 1911 


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TEMPERATURE.  EVAPORATION  FROM  SOIL.  PRECIPITATION  AND 
FLUCTUATION  OF  GROUND-WATER  SURFACE  IN  VALLEY  FLOOR  NEAR  INDEPENDENCE. 

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3 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  203 

region,  it  must  be  exceedingly  slow,  and  it  would  be  entirely  inter- 
cepted by  the  alluvial  fan  of  Lone  Pine  Creek,  which  has  a  ground- 
water surface  higher  than  the  valley  fill  to  the  north.  The  granitic 
formation  of  the  Sierra  Nevada  and  the  granite  core  of  the  Inyo 
Mountains  are  complete  barriers  against  the  escape  of  underground 
waters  through  any  formation  but  the  valley  fill.  It  has  already  been 
shown  that  there  is  no  seepage  flow  into  Owens  Eiver  from  the  water 
supply  of  the  region.  Hence  the  outlets  by  evaporation,  transpiration, 
and  spring  discharge  into  Owens  River  are  all  that  remain  to  be 
considered. 

Soil  evaporation  and  transpiration  will  be  considered,  first,  for  irri- 
gated lands,  and  second,  for  the  general  grass  and  alkali  area  of  the 
valley  floor.  The  quantity  of  water  used  in  irrigating  the  3  Oil  acres 
under  cultivation  in  the  region  is  about  72  sec-ft.  of  continuous  flow 
for  6  months  (Table  18),  which  is  equivalent  to  a  depth  of  8.6  ft.  over 
the  whole  area.  The  depth  of  transpiration  from  alfalfa  during  the 
irrigating  season  has  already  been  computed  as  3.43  ft.,  or  40%  of  the 
total  volume  used.  There  is  also  a  small  loss  through  evaporation 
from  the  soil  during  and  immediately  after  irrigations,  say  0.85  ft., 
or  10%  of  the  total.  The  total  loss  by  evaporation  from  the  soil  and 
by  transpiration  from  irrigated  areas,  therefore,  is  4.3  ft.  in  depth, 
or  18  sec-ft.,  of  continuous  flow. 

The  bases  for  computing  the  evaporation  and  transpiration  loss 
from  grass  and  alkali  land  are  the  soil-evaporation  equations  of 
Fig.  10  and  the  ground-water  contours  of  Plate  V.  The  equations 
were  developed  for  a  fixed  ground-water  surface,  but  they  cover  the 
periods  from  October  1st  to  March  31st  and  from  April  1st  to  Sep- 
tember 30th,  which  practically  coincide  with  the  observed  periods  of 
rising  and  falling  ground- water.  Hence,  to  cover  the  natural  conditions 
of  fluctuating  ground-water  surface,  average  annual  depth  to  ground- 
water at  a  given  point  may  be  substituted  in  the  equations  instead 
of  fixed  ground-water  depths.  The  average  annual  depth  to  ground- 
water, in  feet,  and  the  depth  of  evaporation,  as  determined  from  the 
equations  for  1911,  are  given  in  Table  15  for  the  non-irrigated  areas 
enclosed  by  the  3-ft.  contour  and  between  the  3-  and  4-ft.  and  4-  and 
8-ft.  contours.  The  volume  annually  evaporating  from  the  whole  area 
enclosed  by  these  contours  is  equivalent  to  a  continuous  flow  for  the 
year  of  109  sec-ft. 


204 


SAFE   YIELD   OF   UNDERGROUXD   RESERVOIRS 


TABLE  15.— Total  Evaporation  From  Grass  and  Alkali  Lands  in 

THE  Valley  Floor. 

(Based  on  1911  Data.) 


Area,  in 
square 
miles. 

Average 
depth  to 
ground- 
water, 
in  feet. 

Annual  Depth  of  Evaporation, 
IN  Inches. 

Equivalent 

contours. 

Summer. 

Winter. 

Total. 

second-feet. 

.    .3  Ft 

11,89 
17.6fi 
25.04 

2.5 
3.5 
5.5 

36.5 
29.6 
15.6 

5.2 
4.0 
0.2 

41.7 
33.6 
15.8 

88.6 

3  4  Ft   

43.7 

4-8  Ft 

29.1 

Totals 

54.59 

109.4 

The  water  of  Blackrock  and  Hines  Springs,  and  of  the  small  springs 
along  the  upper  edge  of  the  valley  floor,  spreads  out  in  many  shallow 
lake  basins  before  reaching  Owens  River.  The  loss  by  evaporation 
from  the  surface  of  these  lakes  is  large.  Estimates  based  on  the  area 
of  water  surface  exposed  and  the  evaporation  from  water  in  the 
shallow  pan  in  soil  indicate  that  about  50%  of  the  flow  of  these  springs 
thus  escapes  into  the  atmosphere.  As  the  combined  flow  is  31  sec-ft., 
the  loss  by  evaporation  from  the  free  water  surface  is  15  sec-ft.  The 
portion  of  the  remainder  which  does  not  flow  into  Owens  River  per- 
colates into  the  soil  and  escapes  by  evaporation  from  the  soil  and  by 
transpiration. 

Two  springs  derive  their  waters  from  percolation  and  discharge 
directly  into  Owens  River;  these  are  Upper  and  Lower  Seeley  Springs. 
Their  combined  average  flow  is  11  sec-ft.  In  addition,  the  Blackrock 
Springs  discharge  an  average  of  7  sec-ft.  into  the  river  during  Novem- 
ber to  March,  inclusive,  which  is  equivalent  to  a  continuous  flow  of 
3  sec-ft.  The  total  discharge  into  the  river  from  springs,  therefore, 
is  14  sec-ft. 

The  grand  total  ground-water  losses,  therefore,  are  156  annual 
sec-ft.,  of  which  121  sec-ft.,  or  81%,  is  by  soil  evaporation  and 
transpiration. 

Rate  of  Recharge  by  Percolation. 

From  Precipitation. — All  portions  of  the  region  receive  precipita- 
tion, but  there  is  wide,  local  variation  in  the  quantities  which  enter 
the  ground  and  percolate  downward  to  the  surface  of  saturation.  The 
impei-vious  rock   surfaces  of  the  high  mountain   drainage  areas  shed 


SAFE   YIELD   OF   UXDERGEOUXD   RESERVOIKS  205 

all  precipitation  which  they  receive  except  that  lost  by  evaporation, 
but  accretions  to  the  ground-water  from  precipitation  on  the  remaining 
areas  of  the  region  are  of  considerable  importance. 

Conditions  are  exceptionally  favorable  for  percolation  on  the  inter- 
mediate mountain  slopes.  As  has  been  stated,  the  formation  is  very 
porous,  and  practically  none  of  the  run-off  reaches  living  streams.  All 
precipitation  but  that  lost  by  evaporation,  therefore,  can  be  considered 
as  percolating  downward  to  the  surface  of  saturation  and  becoming 
a  permanent  addition  to  the  ground-water  supply.  Snow  is  practically 
all  melted  before  May  15th,  so  that  the  period  of  direct  exposure  to 
evaporation  is  not  as  long  as  at  higher  levels,  although  the  rate  is 
greater.  Evaporation  losses  from  the  moist  soil  are  very  small. 
Before  it  is  melted,  the  snow  blanket  protects  the  soil  surface,  and 
by  its  gradual  and  uninterrupted  melting  it  fills  the  capillary  spaces 
to  considerable  depth,  so  that  gravity  water  passes  dovmward  rapidly. 
When  the  snow  disappears  the  rapid  drying  of  the  soil  surface  soon 
interrupts  upward  capillary  movement,  thus  preventing  further  evapo- 
ration loss  and  allowing  the  percolating  water  to  reach  the  surface 
of  saturation.  In  view  of  these  facts,  the  percolation  factor  is  regarded 
as  being  about  0.75  for  the  more  elevated  areas  receiving  approximately 
20  in.  of  precipitation.  Less  favored  areas  were  assigned  smaller 
factors  after  a  study  of  their  individual  characteristics. 

The  results  of  computations  of  the  total  quantity  of  percolating 
water  yielded  by  the  intermediate  mountain  slopes  are  shown  in 
Table  16.  The  method  was  to  determine  the  mean  seasonal  precipita- 
tion at  the  center  of  area  of  each  triangular  subdivision,  multiply  this 
by  the  area  in  square  miles,  and  apply  a  percolation  factor.  The  area 
of  each  subdivision  and  the  horizontal  and  vertical  position  of  its 
center  were  obtained  from  Table  3.  Diagrams  7,  8,  10,  11,  13,  and  14 
on  Plate  II  were  used  in  determining  the  depth  of  precipitation.  The 
values  differed  slightly,  as  read  from  the  altitude  and  distance  dia- 
grams, and  the  average  was  adopted  as  the  most  reliable.  The  total 
volume  of  precipitation  on  the  29.4  sq.  miles  of  intermediate  mountain 
slope  is  27  580  acre-ft.,  of  which  19  700  acre-ft.  is  a  permanent  addi- 
tion to  the  underground  water  supply  of  the  region.  Expressed  as  a 
continuous  flow,  the  total  percolation  from  this  area  is  27  sec-ft. 

The  outwash  slopes  yield  to  the  underground  supply  a  much 
smaller  volume  of  water,  which  is  derived  principally  from  slopes  above 


306 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


TABLE    16.— Percolation    From    Precipitation    Upon    Intermediate 
Mountain  Slopes  of  Independence  Region. 
(Mean  seasonal  values.) 
Taboose  Group  of  Precipitation  Gauges. 


Depth  of  Precipitation  on 
Center  of  Area,  in  Inches.* 

Volume  of 

precipitation 

on  area,  in 

acre-feet. 

Percola- 
tion 
factor. 

Quantity  of 
Percolation. 

AdjoinioK  high 

mountain  drainage 

area. 

A. 

B. 

Average. 

Voliime, 
in  acre- 
feet. 

Dis- 
charge, 

in 
second- 
feet. 

22.2 
23.6 
22.2 
18.5 
19.9 

17.8 
17.8 
16.5 
20.0 
15.5 

20.0 
20.7 
19.4 
19.2 
17.7 

2  320 
2  620 
4  080 
2  350 
900 

0.75 
0.75 
0.75 
0.75 
0.70 

1  740 
1  970 
3  060 
1  760 
630 

2.4 

Red  Mountain 

2.7 
4.2 

2.4 

12  270 

9  160 

12.6 

^ 

Oak  Group  of  Precipitation  Gauges. 


18.2 
18.2 
14.5 
16.4 
16.4 
17.7 
18.7 

18.4 
18.9 
15.0 
14.2 
15.8 
15.8 
20.8 

18.3 
18.6 
14.8 
15.3 
16.1 
16.8 
19.8 

1  290 
530 

60 

2  950 
880 

1  810 

3  050 

0.70 
0.70 
0.60 
0.60 
0-70 
0.70 
0.75 

900 

370 

40 

1  770 

620 

1  270 

2  290 

1.2 

Thibaut,  North  Fork. 
Thibaut,  South  Fork. 

Oak,  North  Fork 

Oak,  South  Fork 

.  0.5 
0.1 
2.4 
0.9 

1.8 

3.2 

10  570 

7  260 

10.1 

Pairs  Group  of  Precipitation  Gauges. 


13.4 
12.7 
12.4 
14.8 
15.8 
15.2 

17.0 
12.4 
10.8 
12.0 
15.8 
13.6 

15.2 
12.6 
11.6 
13.4 
15.8 
14.4 

340 
650 
300 
860 
1  760 
830 

0.70 
0.65 
0.65 
0.70 
0.70 
0.70 

240 
420 
200 
600 
1  230 
580 

0.3 

Shepard 

Bairs,  North  Fork — 
Bairs,  South  Fork 

0.6 
0.3 
0.8 
1.7 

0.8 

4  740 

3  270 

4.5 

27  580 

19  690 

27.2 

*  Depth  of  precipitation  as  obtained  by  the  precipitation-altitude  diagram  is  given 
under  A;  as  obtained  by  the  precipitation-distance  diagram  under  B.  The  average  is  taken 
for  use  in  compulations. 

the  5  500-ft.  contour.  Precipitation  occurs  as  snow  less  often  here 
than  on  the  higher  slopes,  and  usually  melts  within  a  few  days  after 
falling.  The  capillary  water  in  the  upper  layers  of  the  soil  thus  has 
opportunity  to  evaporate  after  each  storm,  and  it  is  only  when  several 
storms  occur  in  succession  that  there  is  enough  percolating  water  to 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  207 

penetrate  the  ground  beyond  possibility  of  return.  The  long  dry 
summer  and  the  desert  conditions  draw  all  moisture  from  the  ground 
to  considerable  depths,  and  the  progress  of  percolating  waters  is  slow 
because  the  capillary  spaces  must  be  refilled.  Test  pits  dug  in  the 
region  of  the  4  500-f t.  contour,  10  days  after  a  series  of  storms, 
showed  a  penetration  of  capillary  water  to  a  depth  of  4  ft.  and  the 
entire  absence  of  gravity  water.  The  total  precipitation  from  these 
storms  at  this  point  was  about  3.5  in.,  which,  with  a  28%  available 
pore  space,  would  represent  1  ft.  of  completely  saturated  soil.  Con- 
sidering the  evaporation  losses,  it  is  not  surprising  that  there  was 
no  gravity  water  within  the  depth  of  penetration  observed.  Observa- 
tions made  at  higher  elevations  after  this  storm  showed  gravity  water 
in  considerable  quantity  at  a  depth  of  12  ft.  Percolation  factors 
varying  from  zero  to  0.60  were  assigned  to  the  several  zones  of  the 
outwash  slope  as  a  result  of  these  field  observations. 

The  results  of  computations  for  the  total  quantity  of  percolating 
water  yielded  by  the  outwash  slopes  are  shown  in  Table  17.  The 
whole  area  of  165  sq.  miles  was  divided  into  zones  lying  between  con- 
tours at  500-ft.  intervals  from  about  4  000  to  6  500  ft.,  and  the  zones 
in  turn  were  divided  into  groups  corresponding  with  the  precipitation 
gauges.  The  method  of  computation  was  to  average  the  precipitations 
for  adjacent  contours  obtained  from  Diagrams  7,  8,  10,  11,  13,  and  14 
of  Plate  II.  These  averages  represented  the  average  precipitation 
for  each  zone  in  each  group,  and,  when  multiplied  by  the  area  and 
the  percolation  factor,  gave  the  quantity  of  percolating  water  which 
reached  the  permanent  ground-water  level.  The  total  annual  precipi- 
tation on  the  outwash  slopes  is  62  000  acre-ft.,  of  which  16%,  or 
9  800  acre-ft.,  is  effective  percolating  water.  Expressed  as  a  continu- 
ous flow,  the  volume  of  percolating  water  amounts  to  13.4  sec-ft. 

Throughout  the  valley  floor  the  surface  of  saturation  is  so  close  to 
the  ground  surface  that  capillary  connection  is  maintained  during 
most  of  the  year,  and  percolation  from  precipitation  is  rapid.  The 
depth  of  penetration  is  usually  slight,  however,  because  precipitation 
in  single  storms  is  small.  Several  storms  in  succession  or  a  warm 
rain  on  snow  will  result  in  a  rise  of  ground-water,  but  the  total  average 
ground-water  supply  from  this  source  does  not  exceed  4  sec-ft. 

Direct  percolation  from  precipitation,  therefore,  furnishes  a  grand 
total  of  44  annual  sec-ft.  to  the  underground  supply  of  the  basin. 


308 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 


TABLE  17. — Percolation  from  Precipitation  Upon  Outwash  Slopes 
OF  THE  Independence  Region. 
(Mean  seasonal  values.) 
Taboose  Group  of  Precipitation  Gauges. 


Area  of 
zones, 

in 
square 
miles. 

Depth  of  Precipi- 
tation, IN  Inches. 

Volume 

of 
precipi- 
tation 
on  zone, 
in  acre- 
feet. 

Percola- 
tion 
factor. 

Quantity  of 
Percolation. 

Contours  bounding 

precipitation 

zones. 

On  con- 
tours. 

On  zone. 

Volume, 
in  acre- 
feet. 

Dis- 
charge, 

in 
second - 

feet. 

Grass-4  500 

28.07 
8.54 
8.14 
5.56 
3.42 

6.0,     7.7 
7.7,     9.0 
9.0.   10.8 

10.8,  12.9 

12.9,  15.2 

6.8 
8.4 
9.9 
11.8 
14.0 

10  180 

3  830 

4  300 
3  500 
2  550 

O.OO 
0.10 
0.20 
0.35 
0.60 

0 

380 

860 

1  220 

1  530 

0 

4  500-5  OOO 

0.5 

5  OCO  5  500 

1.2 

5  500-6  000 

1.7 

6  000-6  500 

2.1 

53.73 

24  360 

3  990 

5.5 

Oak  Group  of  Precipitation  Gauges. 


Grass-4  500 

4  .500-5  000. 

5  000-5  500. 

5  500-6  000. 

6  000-6  500. 


24.57 
11.78 
9.23 

5.82 
4.82 


56.22 


4.8,     5.9 

5.4 

7  080 

0 

0 

5.9,     7.3 

6.6 

4  150 

0.05 

210 

7.3,     9.1 

8.2 

4  040 

0.15 

610 

9.1,   11.3 

10.2 

3  170 

0.30 

950 

11.3.  13.6 

12.4 

3  190 

0.50 

1  600 

21  630 

3  370 

0 

0.3 

0.8 

1.3 

2.2 


4.6 


Pairs  Group  of  Precipitation  Gauges. 


Grass-4  500 

19.56 
11.68 
9.76 

8.3,     4.0 
4.0,     5.2 
5.2,     6.9 
6.9,     8.6 
8.6,   10.3 

3.6 
4.6 
6.0 

7.8 
9.4 

3  760 

2  860 

3  120 
3  840 
2  560 

0 

0 

0.10 

0.25 

0.45 

0 

0 

810 

960 

1  150 

0 

4  500  5  000 

0 

5  000-5  500 

0.4 

5  500-6  000 

9.23 

1.3 

6  000  6  500 

5.11 

1.6 

55.34 

16  140 

2  420 

3.3 

165.29 

62  130 

9  780 

13.4 

From  Stream  Channels. — The  most  important  source  of  under- 
ground water  in  a  desert  region  is  percolation  from  stream  channels. 
This  process  is  continuous  from  perennial  streams,  although  it  varies 
with  the  discharge  of  the  streams  and  the  temperature,  as  previously 
indicated.  Beneath  each  stream  channel  as  it  crosses  the  outwash  slope 
is  a  "ridge"  of  ground-water  rising  from  the  general  plane  of  satura- 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  309 

tion.  The  inclination  of  the  slopes  of  this  ridge  and  the  breadth  of 
its  base  vary  periodically  with  the  stage  of  the  creek  and  the  time  of 
year.  There  is  complete  saturation  within  its  slopes  and  a  movement 
of  gravity  water  toward  the  general  ground-water  surface.  A  consid- 
erable quantity  of  water  also  percolates  from  intermittent  streams. 

Percolation  from  stream  channels  in  the  Independence  Basin  is 
confined  to  the  creeks  draining  mountain  canyons.  There  are  17  of 
of  these  streams,  11  of  which  are  perennial  throughout  their  channels, 
5  are  perennial  over  the  upper  portion  of  their  channels  only,  and  1 
(Dry  Canyon)  is  entirely  an  underground  stream.  The  surface  flow 
of  the  two  most  northerly  of  these  streams,  Tinemaha  and  Red 
Mountain  Creeks,  discharges  northward  across  the  Poverty  Hills  into 
the  Bishop-Big  Pine  region,  but  the  percolation  from  their  channels 
is  tributary  to  the  Independence  Basin.  The  channels  of  streams  en- 
tirely within  the  basin  are  continuous  from  their  canyons  to  the  U.  S. 
Geological  Survey  gauging  stations,  below  which  they  divide,  irriga- 
tion ditches  carrying  all  the  flow  except  during  the  high-water  period 
of  wet  years,  when  the  excess  passes  down  the  natural  channels.  The 
problem  is  thus  divided  into  the  determination  of  percolation  above 
and  below  the  Government  gauging  stations.  The  first  subject  has 
already  been  discussed  at  length  and  need  not  be  considered  here  in 
detail.  An  inspection  of  Tables  4  and  5  shows  that  for  the  creeks  from 
Taboose  to  Hogback,  inclusive,  the  total  21-year  average  discharge  at 
the  mouths  of  the  canyons  is  130  sec-ft.  and  at  the  Government 
gauging  stations  84  sec-ft.  If  the  flow  of  2  sec-ft.  from  Spring  No.  2 
on  Division  Creek  is  included  with  the  canyon  discharge,  the  percola- 
tion loss  above  the  Government  gauging  stations  is  48  annual  sec-ft. 
To  this  should  be  added  6  sec-ft.,  as  indicated  by  the  diagrams,  for 
Tinemaha  and  Red  Mountain  Creeks,  making  a  total  of  54  sec-ft. 

The  quantity  lost  below  these  stations  is  not  so  easily  determined, 
on  account  of  the  numerous  channels  and  irregular  flow.  Estimates 
were  made  on  each  creek,  based  on  the  length  of  main  channel  and  dis- 
tributing ditches  outside  of  irrigated  areas.  The  loss  per  mile  was  as- 
sumed to  be  the  average  annual  loss  per  mile  for  the  upper  channel 
of  the  creek,  and  the  total  percolation  loss  from  stream  channels  below 
the  Government  stations  was  estimated  at  25  sec-ft.  of  continuous  flow. 
This  estimate  does  not  include  percolation  from  waste  irrigation  water 
or  surplus  creek  water  which  has  passed  east  of  the  ranches. 


210 


SAFE   YIELD   OF   UNDEEGROUN^D   RESERVOIRS 


The  grand  total  addition  to  the  underground  supply  derived  by 
percolation  from  stream  channels,  therefore,  is  79  annual  sec-ft. 

From  Irrigation. — Irrigation  -has  been  practised  throughout  this 
region,  in  connection  with  farming,  for  at  least  30  years,  and  is  a 
permanent  factor  in  the  underground  water  problem.  The  total  area 
under  systematic  irrigation  is  approximately  3  000  acres,  divided  into 
a  number  of  isolated  ranch  groups  which  depend  on  the  mountain 
creeks  for  their  supply.  Oak  Creek,  the  largest  of  these  streams,  sup- 
plies about  45%  of  the  whole  area.  The  remaining  area  is  divided 
among  eight  creeks  and  the  Stevens  ditch,  which  during  the  period  of 
observation  has  been  largely  supplied  by  the  surplus  flow  of  the 
creeks.  The  acreage  irrigated  from  each  source  is  given  in  Table  18. 
About  50%  of  this  land  was  originally  desert,  lying  along  the  lower 
margin  of  the  outwash  slope,  and  is  very  porous.  The  remainder  lies 
in  the  valley  floor,  where  permanent  ground-water  is  within  reach  of 
plant  roots  and  where  clay  soils  predominate.  The  location  of  the 
several  areas  is  shown  on  Plate  V.     Alfalfa  and  grain  are  irrigated  by 

TABLE  18. — Estimated  Net  Volume  of  Water  Used  for  Irrigation 
IN  THE  Independence  Eegion  During  1909. 


Source  of  supply. 


Area  irri- 
gated, in 
acres.  * 


Duty  of 

water  per 

acre  for 

season, 

acre-feet,  t 


Total  Volume  of 
Water  Used. 


Acre-feet. 


Second- 
feet  for 
6  months. 


Taboose  Creek 

Goodale  Creek 

Division  Creek 

Sawmill  Creek 

Oak  Creek,  ranch  No.  1 
Oak  Creek,  ranch  No.  2 
Oak  Creek,  ranch  No.  3 
Oak  Creek,  ranch  No.  4 
Oak  Creek,  ranch  No.  5 

Oak  Creek 

Oak  Creek 

Oak  Creek 

Little  Pine  Creek 

Symmes  Creek 

Shepard  Creek 

George  Creek 

Stevens  ditch 


(170) 
(110) 
(  80) 
(  90) 

109 
49 

155 


(  80) 
(100) 
(560) 
(300) 
(160) 
(280) 
(160) 
(310) 


(12) 

(16) 

(16) 

(16) 
7.22 
15.40 
2.80 
2.34 
16.40 

(16) 

(  5) 

(  3) 

(14) 

I  5) 

(12> 

(12) 

(8) 


760 


1  440 
790 
758 
435 
609 
623 

1  -^80 
500 

1  680 

4  200 
8fj0 

3  360 

1  920 

2  480 


5.6 
4.9 
3.5 
4.0 
2.2 
2.1 
1.2 
1.7 
1.7 
3.5 
1.4 
4.6 
11.6 
2.2 
9.3 
5.3 
6.9 


3  Oil 


25  955 


71.7 


*  Areas  in  parentheses  obtained  from  approximate  field  observations;   other  areas 
obtained  by  careful  field  measurement. 

I  Figures  in  parentheses  assumed  from  observations  on  Oak  Creek  ranches. 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  211 

flooding,  and  corn  by  the  furrow  method.  Three  crops  of  alfalfa  are 
raised  each  year,  and  the  irrigating  season  extends  from  about  April 
15th  to  October  15th,  although  some  farmers  irrigate  9  months  in  the 
year.  Grain  is  irrigated  early  in  the  season,  and  corn  late,  so  that 
the  water  is  continually  used.  In  most  places  the  use  of  water  is 
lavish,  and  no  attempt  is  made  to  economize  it  or  even  to  apply  the 
quantity  best  suited  to  the  crop  and  soil  conditions. 

A  basis  for  determining  the  percolation  from  irrigation  is  a  knowl- 
edge of  the  duty  of  water,  or  the  quantity  of  water  used  in  maturing 
a  given  area  of  crop.  This  was  obtained  in  1909  by  carefully  measur- 
ing the  quantity  of  water  used  daily  during  the  irrigating  season  on 
five  typical  ranches  which  derived  their  supply  from  Oak  Creek.  On 
ranches  where  there  was  a  continual  waste  from  irrigation  the  surplus 
water  was  also  measured.  Areas  in  crop  were  obtained  from  a  careful 
stadia  survey  of  each  ranch. 

With  conditions  on  these  typical  ranches  in  mind,  an  examination 
was  made  of  all  other  ranches  in  the  region,  and  values  were  estimated 
for  the  duty  of  water  on  each.  The  number  of  acres  irrigated  and  in 
crop  was  also  determined  approximately  by  reference  to  subdivisions 
of  the  public  survey.  From  these  data  the  volume  of  water  used  for 
irrigation  was  determined,  as  shown  in  Table  18.  The  total  volume 
used  during  the  6  months,  April  15th  to  October  15th,  is  about  26  000 
acre-ft.,  equivalent  to  a  continuous  flow  of  72  sec-ft.  during  the  period. 
When  spread  out  over  3  010  acres,  this  represents  an  average  depth  of 
8.6  ft.  This  result  probably  represents  an  average  practice  throughout 
the  Owens  Valley,  for  the  duty  of  water  measured  by  the  Eeclamation 
Service  during  the  season  of  1904  on  two  typical  ranches  near  Bishop 
was  Y.ll  and  9.17  acre-ft.  per  acre. 

The  distribution  of  this  water,  as  regards  evaporation,  transpiration, 
and  percolation  beyond  the  reach  of  plant  roots,  is  the  next  step  in 
computing  the  ground-water  supply  from  this  source.  Direct  evapora- 
tion is  relatively  small,  for  the  water  when  spread  out  over  the  fields 
is  shaded  by  the  crop  and  sinks  rapidly  into  the  ground.  Probably 
10%  would  cover  this  loss.  The  transpiration  loss  from  alfalfa  during 
the  irrigation  season  has  already  been  computed  as  3.43  ft.  depth  of 
equivalent  water,  or  40%  of  the  average  volume  of  water  applied  to 
crops.  The  transpiration  loss  from  corn  and  small  grains  is  probably 
less  in  this  locality,  but  the  direct  evaporation  loss  is  greater.     There- 


212  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

fore  50%,  or  4.3  ft.  depth,  represents  the  quantity  of  water  applied  in 
irrigation  in  this  region  which  is  absorbed  by  the  atmosphere.  The 
other  50%  is  a  permanent  addition  to  the  ground-water  supply,  and  is 
equivalent  to  a  continuous  flow  of  18  sec-ft.  throughout  the  year. 

From  Flood  Water. — The  quantity  of  percolation  from  surplus 
creek  water,  which  spreads  out  over  the  valley  floor  to  a  greater  or  less 
extent,  is  difiicult  to  determine.  Of  the  84  sec-ft.  average  flow  at  Gov- 
ernment gauging  stations,  61  sec-ft.  are  disposed  of  in  channel  perco- 
lation and  irrigation.  Possibly  5  sec-ft.  of  the  remainder  reach  Owens 
River.  This  leaves  18  sec-ft.  to  be  divided  between  evaporation  and 
percolation  in  the  flats  between  the  ranches  and  the  river.  The  area 
flooded  averages  about  5  sq.  miles  during  June  and  July.  The  loss 
by  evaporation  during  this  period  from  a  shallow  pan  in  soil  was 
about  24.5  in.,  and,  as  the  conditions  are  similar,  this  represents  ap- 
proximately the  loss  from  shallow  flood  water.  The  volume  expressed 
as  a  continuous  flow  for  two  months  is  55  sec-ft.,  or,  for  a  year,  9  sec- 
ft.  The  other  9  sec-ft.  can  be  assumed  to  represent  the  percolation 
from  this  flood  water.  It  is  not  a  permanent  addition  to  the  ground- 
water supply,  however,  for  the  surface  of  saturation  is  only  a  few  feet 
below  the  ground  surface  in  this  area,  and  evaporation  from  damp  soil 
and  transpiration  from  natural  vegetation  soon  reduce  the  ground- 
water surface  to  its  normal  position. 

Summary  of  Percolation. — The  four  sources  of  ground-water  are 
percolation  from  direct  precipitation,  from  stream  flow,  from  irriga- 
tion, and  from  flood  water  in  the  valley  floor. 

The  first  of  these  yields  about  44  annual  sec-ft.,  of  which  61%  is 
from  the  intermediate  mountain  slopes,  30%  from  the  outwash  slopes, 
and  9%  from  the  valley  floor.  Percolation  from  streams  yields  about 
79  annual  sec-ft.,  of  which  68%  is  above  Government  gauging  stations 
and  32%  below.  Irrigation  yields  18  annual  sec-ft.  and  flood  waters 
in  the  valley  floor  9  annual  sec-ft. 

The  grand  total  ground-water,  therefore,  is  150  annual  sec-ft.,  of 
which  probably  75%  reaches  the  deeper  strata  of  the  valley  fill.  The 
rate  of  recharge  of  the  basin,  as  thus  determined,  differs  by  less  than 
4%  from  the  ground-water  loss  previously  computed.  The  reliability 
of  the  data  is  thus  confirmed  as  well  as  the  correctness  of  the  assump- 
tions. 


safe  yield  of  underground  reservoirs  213 

Safe  Yield. 

Thus  far,  this  paper  has  presented  conditions  as  they  are  found  to 
exist  in  a  natural  state.  The  problems  which  the  engineer  has  to  solve 
are  those  connected  with  the  artificial  extraction  of  water  from  under- 
ground reservoirs.  First  among  these  is  the  determination  of  the  safe 
annual  yield  or  the  limit  to  the  quantity  of  water  which  can  be  with- 
drawn regularly  and  permanently  without  dangerous  depletion  of  the 
storage  reserve.  A  second  problem  which  naturally  accompanies  the 
first  is  the  devising  of  methods  for  increasing  artificially  the  safe  annual 
yield  of  reservoirs  which  are  apparently  already  developed  to  the  limit. 
The  writer  will  outline  his  ideas,  in  the  hope  that  they  will  suggest  a 
constructive  line  of  discussion  which  will  lead  to  a  better  understanding 
of  these  subjects. 

It  is  obvious  that  water  permanently  extracted  from  an  underground 
reservoir,  by  wells  or  other  means,  reduces  by  an  equal  quantity  the 
volume  of  water  passing  from  the  basin  by  way  of  natural  channels. 
This  is  illustrated  by  the  commonly  recognized  fact  of  the  drying  up 
of  springs  and  cienagas  as  the  result  of  heavy  pumping.  The  theoreti- 
cal limit  for  safe  draft,  exclusive  of  return  water,  therefore,  is  the 
average  rate  of  recharge  for  a  basin.  The  practical  limit,  however, 
depends  on  the  relation  of  draft  to  storage  capacity,  within  economic 
pumping  limits.  Where  the  storage  capacity  is  very  large  as  compared 
with  annual  draft,  the  theoretical  and  practical  limits  should  nearly 
agree,  as  the  storage  reserve  can  be  drawn  on  in  periods  of  protracted 
drought.  For  basins  with  comparatively  small  storage  capacity,  the 
practical  limit  will  be  less  than  the  theoretical.  Draft  computations 
may  be  made  with  the  mass-diagram  as  ordinarily  used  in  surface 
storage  problems.  Storage  capacity  is  determined  from  the  area 
of  water-bearing  material,  limiting  depth  for  economic  pumping, 
and  percentage  of  voids  capable  of  depletion.  The  supply  is  the  quan- 
tity of  water  annually  absorbed  by  the  porous  material  of  the  basin. 
This  may  be  determined  each  year  by  methods  similar  to  those  used 
in  the  Owens  Valley  studies. 

The  draft  thus  obtained,  however,  is  not  the  safe  yield  of  the 
basin,  for  there  are  always  certain  residual  losses  which  cannot  be 
entirely  prevented,  such  for  instance  as  soil  evaporation  from  cienaga 
lands.  These  residual  losses  must  be  ascertained  and  deducted  from 
the  gross  draft.     The  quantity  thus  obtained  may  be  persistently  with- 


214  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

drawn  from  the  basin  without  causing  general  depression  of  the  water 
plane  to  the  point  where  pumping  operations  must  cease  for  economic 
reasons. 

The  determination  of  residual  losses  presents  difficult  problems. 
Some  of  the  conditions  which  are  responsible  for  these  losses  are  the 
following: 

1. — The  elevation  of  the  impervious  rim  at  the  outlet  being  less 
than  the  elevation  of  the  water  plane  in  the  lowest  depression  of  the 
basin,  thus  allowing  ground-water  to  escape  as  underflow.  The  quan- 
tity of  water  thus  dissipated  depends  on  the  transmission  capacity 
and  area  of  the  porous  material  overlying  the  rim  and  the  available 
head.  In  most  cases  the  volume  of  water  thus  lost  is  relatively  very 
small. 

2. — The  outlet  of  springs  being  at  a  considerably  lower  elevation 
than  the  general  water  plane  of  the  basin  in  the  outlet  region.  Such  a 
condition  may  exist  where  an  arroya  has  cut  a  channel  through  the 
impervious  rim  at  a  point  where  the  surface  falls  away  rapidly  down 
stream.     Such  losses  are  also  relatively  small. 

3. — The  occurence  of  water  under  Artesian  pressure  in  underlying 
strata  of  porous  material  confined  between  more  impervious  layers  of 
fine  sand  or  clay.  This  is  the  least  recognized,  but  yet  the  most  im- 
portant, cause  of  residual  ground-water  loss.  The  effect  of  Artesian 
pressure  is  to  force  moisture  through  pores  or  fractures  in  the  im- 
pervious capping  and  thus  maintain  a  permanent  ground-water  plane 
near  the  surface.  The  water  continually  supplied  from  below  is  dis- 
posed of  either  by  evaporation  from  the  soil  surface  and  vegetation  or 
by  escaping  at  the  surface  in  springs  or  seepages.  These  losses  persist 
as  long  as  the  Artesian  pressure  is  sufficient  to  force  the  water  through 
the  overlying  strata.  The  volume  of  these  losses  during  any  period  of 
one  or  more  years  bears  a  functional  relation  to  the  average  Artesian 
pressure  during  the  same  period.  The  writer  states  these  conclusions 
85  the  result  of  a  careful  study  of  records  and  conditions  in  a  number 
of  differently  situated  Artesian  basins. 

These  conclusions  are  well  illustrated  by  the  following  facts  of 
common  knowledge.  First,  consider  the  result  of  abnormally  large 
precipitation  for  a  period  of  one  or  more  seasons.  The  ground-water 
accretions  exceed  the  losses  from  the  basin,  the  excess  water  accumu- 
lates in  the  voids  of  the  porous  gravels  surrounding  the  confined  strata, 


SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS  215 

and  the  free  ground-water  surface  rises  throughout  the  basin.  Within 
the  area  of  confined  gravels  hydrostatic  or  Artesian  pressure  increases. 
A  greater  quantity  of  water  is  forced  through  the  overlying  strata,  not 
only, over  the  area  already  moist,  but  from  a  circumscribing  zone 
within  which  the  pressure  was  previously  insufficient  to  maintain  a 
shallow  ground-water  surface.  The  observed  result,  therefore,  is  in- 
creased spring  and  seepage  flow  and  an  enlarged  area  of  moist  cienaga 
land  from  which  evaporation  occurs.  Second,  assume  a  series  of  dry 
years.  Ground-water  storage  is  depleted,  the  free  ground-water  plane 
falls,  Artesian  pressure  decreases,  and  less  water  is  forced  through  the 
overlying  strata.  The  observed  result  is  decreased  spring  and  seepage 
flow  and  shrunken  evaporating  area.  The  latter  occurs,  because,  for 
the  new  conditions,  the  rate  of  evaporation  from  the  outer  zone  of 
moist  soil  exceeds  the  rate  of  supply  from  below.  The  accumulation 
of  water  in  the  soil  is  drawn  on,  lowering  the  water  level  to  the  limit 
of  capillary  action.  A  similar  result  occurs  where  relief  is  afforded 
to  Artesian  pressure  by  the  drilling  of  many  deep  wells  drawing  from 
Artesian  strata.  In  some  of  the  Southern  California  Artesian  basins, 
which  formerly  possessed  cienaga  lands,  relief  of  Artesian  pressure 
by  wells  and  heavy  pumping  has  dried  up  such  lands. 

The  importance  of  residual  losses,  due  to  Artesian  pressure,  is 
forcibly  shown  by  the  Owens  Valley  studies,  where  it  was  found  that 
in  a  natural  state  81%  of  the  total  yield  of  the  Independence  Basin 
was  lost  by  evaporation  from  soil  and  vegetation.  Similar  conditions, 
in  a  slightly  less  degree,  existed  in  many  of  the  Southern  California 
basins  before  ground-water  development  was  undertaken.  The  in- 
creased pumping  of  the  last  10  or  15  years  has  eliminated  evaporation 
losses  almost  entirely  in  some  of  the  smaller  basins.  In  the  larger 
basins,  such  as  the  San  Bernardino  Valley  and  Coastal  Plain,  the  re- 
duction has  not  been  as  great,  having  ranged  from  30  to  50%  of 
original  evaporation  losses  in  the  various  basins.  In  these  basins 
evaporation  losses  formerly  represented  from  50  to  75%  of  the  total 
ground-water  supply.  Hence,  the  residual  evaporation  losses  to-day 
represent  from  15  to  35%  of  the  total  ground-water  supply  for  the 
large  Southern  California  basins,  and  can  be  said  to  average  25  per 

cent. 

The  quantitative  determination  of  the  residual  losses  from  an  un- 
derground reservoir  can  only  be  made  after  a  detailed  study  of  the  local 


210  SAFH   YIELD   OF   UNDERGROUND   RESERVOIRS 

conditions.  The  factors  to  be  considered  are  the  topography  and 
geology  of  the  basin  and  its  porous  filling,  the  distribution  and  type 
of  sources  of  percolating  water,  the  rate  of  evaporation  and  transpira- 
tion, the  depth  of  capillary  action  and  the  character  of  the  soil  within 
the  evaporating  area,  the  necessity  for  irrigation  and  the  value  of  over- 
lying lands  for  agricultural  crops,  the  present  or  probable  ultimate 
method  of  development  of  water,  and  the  present  or  probable  future 
use.  The  general  condition  favorable  for  small  residual  losses  is  the 
possibility  of  eliminating  the  evaporating  area  by  lowering  the  water 
plane  below  the  reach  of  capillary  action.  This  may  be  done  by  the 
relief  of  Artesian  pressure,  by  shallow  pumping  within  the  evaporating 
area,  or  by  drainage.  The  first  of  these  methods  would  result  in  re- 
duced pressures  in  existing  wells  in  the  Artesian  area  and  possibly 
lowered  water  levels  in  the  back-water  zone,  especially  if  the  ground 
surface  has  a  steep  slope.  Shallow  pumping  and  drainage,  on  the  other 
hand,  may  be  physically  impractical  or  prohibitive  in  cost.  Their  suc- 
cess depends  largely  on  the  existence  of  shallow  water-bearing  strata 
from  which  water  can  be  readily  drawn. 

There  are  three  cases  which  arise  in  the  determination  of  residual 
losses :  first,  a  basin  already  fully  developed  or  suffering  from  over- 
draft; second,  a  basin  where  the  supply  is  partly  developed;  third,  a 
basin  entirely  undeveloped.  The  first  case  can  be  recognized  by  in- 
spection of  the  present  or  former  evaporating  area  in  connection  with 
local  confirmatory  evidence  and  past  records  of  water  levels,  yield  of 
wells,  etc.  The  residual  losses  may  be  ascertained  from  observations 
and  measurements  of  existing  conditions.  The  second  and  third  cases 
require  assumptions  as  to  the  method  or  combination  of  methods  by 
which  residual  losses  will  be  reduced  to  a  minimum.  These  assump- 
tions should  be  made  after  a  careful  study  of  local  physical  condi- 
tions and  the  probable  future  use  of  the  water.  The  next  step  is  the 
determination  of  existing  evaporation  losses,  by  contouring  the 
ground  surface  and  water  plane,  and  ascertaining  the  soil  evaporation 
losses  for  various  depths  to  ground-water.  The  final  step,  namely,  the 
determination  of  the  percentage  by  which  existing  losses  will  be  re- 
duced by  future  development,  is  as  yet  largely  a  matter  of  judgment. 
Having  arrived  at  some  definite  value,  however,  the  residual  losses  due 
to  evaporation  can  be  computed,  and,  when  combined  with  the  losses 
from  underflow  or  deep  springs,  the  total  quantitative  result  is  obtained. 


SAFE    YIEI.D   OF   UXDERGHOUXD   RESERVOIRS  217 

The  thorough  investigation  of  residual  losses  is  essential  in  any  de- 
termination of  safe  yield,  and  for  this  reason  the  writer  has  discussed 
the  subject  in  detail. 

Passing  now  from  the  determination  of  safe  yield  as  limited  by 
existing  conditions  to  a  discussion  of  methods  for  increasing  safe  yield 
artificially:  Obviously,  to  accomplish  the  latter,  either  the  rate  of  re- 
charge of  the  basin  must  be  increased  or  the  percentage  of  unused 
water  escaping  from  the  basin  must  be  decreased.  Practical  methods 
which  suggest  themselves  are : 

(1)  Reduction  of  residual  losses  to  the  lowest  possible  quantity; 

(2)  Elimination  of  needless  waste  of  underground  water;  and 

(3)  Increased  absorption  of  surface  flood  waters. 

The  subject  of  residual  losses  has  already  been  discussed  at  length. 
The  writer  -wishes  to  emphasize  the  fact,  however,  that  a  basin  has 
not  been  fully  developed  as  long  as  the  evaporating  area  persists  in 
years  of  drought.  The  evaporating  area  is  fully  as  important  a  cri- 
terion of  the  relation  of  withdrawals  to  supplj'^  as  the  water  plane.  A 
falling  water  plane  does  not  of  itself  indicate  overdraft.  It  is  only 
when  a  rapid  shrinkage  and  disappearance  of  the  evaporating  area 
accompanies  a  falling  water  plane  that  dangerous  overdraft  is  indi- 
cated. Hence,  in  a  closed  Artesian  basin  from  which  the  evaporation 
area  has  not  disai:)pea.red,  a  greater  yield  may  be  obtained,  provided 
an  intelligent  plan  of  development  is  followed. 

A  very  common  source  of  needless  waste  is  from  Artesian  wells 
which  are  allowed  to  flow  when  the  water  is  not  in  use.  The  waste- 
fulness of  this  practice  is  so  evident  that  it  need  not  be  discussed  in 
this  paper.  Its  continuance  is  made  possible  by  lack  of  recognition 
of  the  ultimate  effect  of  the  practice  among  the  owners  of  such  wells. 
The  writer  feels  that  it  is  every  engineer's  duty  and  privilege  to  as- 
sist in  guiding  aright  public  opinion  in  matters  of  common  interest, 
and  suggests  the  subject  of  conservation  of  Artesian  water  as  being 
pertinent  in  many  communities. 

The  practicability  of  increasing  the  ground-water  supply  by  bring- 
ing about  greater  absorption  of  flood  water  has  been  demonstrated  in  a 
number  of  California  basins.  The  most  extensive  work  of  this  kind 
is  probably  that  done  on  the  alluvial  cone  of  Santa  Ana  River  in  the 
San  Bernardino  Valley.     The  method  there  used  is  to  divert  the  flood 


218  SAFE   YIELD   OF   UNDERGROUND   RESERVOIRS 

water  of  Santa  Ana  River  in  contour  ditches  from  which  it  is  dis- 
tributed into  smaller  ditches  which  in  turn  subdivide,  until  finally 
the  water  spreads  out  over  the  porous  alluvial  gravels  in  a  thin  sheet 
and  is  absorbed.  During  the  past  few  years  the  volume  of  water  thus 
stored  has  averaged  12  000  acre-ft.  annually,  costing  about  15  cents 
per  acre-ft.,  including  interest  on  the  cost  of  permanent  works.  The 
work  is  capable  of  further  expansion.  The  ultimate  limit  will  be  the 
ability  to  handle  the  violent  floods,  which  are  of  frequent  occurrence. 
The  problem  is  not  that  alone  of  controlling  the  water,  but  of  dispos- 
ing of  silt.  The  water  is  normally  clear  and  is  free  from  silt  soon 
after  the  flood  crest  passes.  Flood  water,  however,  carries  great  quan- 
tities of  silt,  which  deposits  as  soon  as  the  velocity  is  checked.  This 
forms  an  impervious  layer  of  slime  which  seals  the  gravels  and  must 
be  broken  up  and  eventually  removed  in  order  to  use  the  same  spread- 
ing ground  continuously. 

The  conditions  on  most  California  streams  tributary  to  closed 
basins  correspond  to  the  Santa  Ana.  The  writer  is  of  the  opinion 
that  complete  absorption  of  even  ordinary  floods  on  these  streams 
cannot  be  brought  about  without  temporary  surface  storage.  This  must 
be  accomplished  either  by  utilizing  storage  sites  in  the  stream  channel 
or  by  construction  of  contour  levees  on  the  alluvial  cone.  The  purpose 
of  such  reservoirs  would  be  to  act  both  as  settling  basins  and  as  tem- 
porary storage  sites.  From  these  reservoirs  the  clear  water  would  be 
released  and  brought  into  contact  with  the  absorbent  gravels  by  any 
method  which  proved  most  efficient  under  the  local  conditions. 

In  conclusion  it  may  be  said,  first,  that  the  rate  of  recharge  of  un- 
derground reservoirs  of  the  closed-basin  type  is  a  definite  quantity 
capable  of  measurement  with  a  fair  degree  of  accuracy;  second,  that 
safe  yield  is  a  quantity  less  than  the  rate  of  recharge,  its  quantity  de- 
pending on  the  available  storage  reserve  of  the  basin  and  residual 
ground-water  losses;  third,  that  imder  certain  circumstances  it  is  pos- 
sible to  increase  the  safe  yield  of  a  fully  developed  basin. 


DISCUSSION  :    YIELD  OF   UNDERGROIXD   RESERVOIRS  219 

DISCTJSSI  ON 


James  Owen  *  M.  Am.  Soc.  C.  E.— Although  Mr.  Lee's  paper  is    Mr. 

T         •         1  Owen, 

confined    somewhat    to    underground    water    supphes    m    the    western 

part  of  the  United  States,  a  great  deal  of  investigation  has  been  done 
and  a  great  deal  of  money  has  been  spent  and  wasted  on  such  sup- 
plies in  the  eastern  sections  and  in  localities  near  New  York  City, 
and  it  seems  that,  if  it  were  possible  in  the  future  to  define  certain 
rules  and  principles  governing  the  question  of  getting  water  from 
the  ground,  it  would  be  better  for  everybody. 

The  section  around  New  York  has  a  variety  of  topographical  and 
geological  conditions.  According  to  the  speaker's  idea,  the  under- 
ground supplies  can  be  defined  under  about  four  heads,  that  is,  the 
original  sandstone  deposition,  prior  to  the  volcanic  upheaval;  the 
volcanic  upheaval  of  gneiss  in  Westchester  County  and  New  York, 
and  the  trap  in  New  Jersey;  the  glacial  and  post-glacial  depositions, 
and,  incidental  to  these,  the  terminal  moraines;  and  finally,  in  lower 
New  Jersey,  what  might  be  called  the  post-tertiary  deposition.  The 
first  and  the  last,  the  original  sedimentary  deposition  of  the  sandstone 
and  the  post-tertiary  deposition,  have  fairly  well-defined  radii  of 
supply. 

It  is  well  known  that  water  can  usually  be  obtained  by  driving 
through  sandstone.  In  New  Jersey,  if  one  drives  through  certain 
strata,  water  can  be  obtained,  and  an  interesting  incident  was  shown 
when  Asbury  Park,  N.  J.,  desired  a  water  supply  and  was  advised 
by  Professor  Gay,  State  Geologist  of  New  Jersey  30  years  ago,  to  go 
down  800  ft.,  at  which  depth  all  the  necessary  water  could  be  obtained. 
On  trial,  water  was  found  within  40  ft.  The  final  result  has  been 
that  all  through  that  shore  territory  the  supply  of  water  has  been 
ample,  good,  and  economical.  In  this  section,  however,  the  main  con- 
sumption has  only  lasted  about  4  months  in  the  year,  and  during  the 
other  8  months,  the  disposal  of  the  underground  supply  would  have 
failed  to  be  profitable  for  steady  communities. 

In  the  sandstone  formation,  a  good  and  reliable  supply  can  always 
be  obtained,  subject  to  the  chemical  and  natural  properties  of  the 
water.  In  New  Jersey,  wells  have  been  sunk  400  or  500  ft.  below 
tidewater  and  ample  water  has  been  found,  but  its  chemical  constitu- 
ents have  made  it  rather  detrimental  for  public  use.  In  one  case, 
where  the  well  was  put  down  400  ft.,  the  deposition  of  lime  was  about 
8  in.  in  4  months.  That,  of  course,  debarred  its  use  for  public  pur- 
poses. The  water,  however,  was  storage  water,  and  the  slow  per- 
colation through  the  sandstone  had  not  allowed  for  a  free  flow;  con- 
sequently, the  chemical  deposition  ensued. 

*  Newark,  N.  J. 


220  DISCISSION  :  yield  of  I'XDERGROI-XD  resebvotes 

Mr.  In  the  other  two  regions,  the  volcanic  and  the  post-glacial  forma- 

'^*^°'  tions,  there  is  a  certain  amount  of  uncertainty  in  regard  to  the  supply. 
In  the  volcanic  formation  with  a  slight  cover,  of  course,  there  is  no 
water  unless  one  goes  into  the  rock;  and  in  either  the  trap,  gneiss, 
or  Atlantic  formation,  the  supply  is  uncertain,  erratic,  and  unreliable, 
and  very  rarely  successful. 

In  the  post-glacial  formation,  the  drifts  fill  up  the  subterranean 
canals,  as  they  may  be  called,  and  the  terminal  moraine  depositions. 
In  this  case  the  water  supply  is  fairly  reliable  within  certain  limits. 
In  the  speaker's  experience  there  have  been  two  or  three  curious 
propositions  relating  to  this  question.  A  certain  city  put  in  a  water 
plant  in  a  post-glacial  deposition.  When  the  wells  were  put  down 
they  overflowed.  Pipes  were  driven  down  80  or  100  ft.,  and  left 
up  in  the  air  10  or  15  ft.,  and  still  the  wells  overflowed.  The  pumping 
plant  was  started,  and,  of  course,  the  overflow  was  gradually  lowered. 
Incidental  to  that  was  the  fact  that,  a  little  above  the  pumping  plant, 
a  man  owned  a  very  heavy  spring  which  was  totally  stopped  after  a 
short  period  of  pumping.  He  brought  suit  against  the  company,  and, 
by  a  curious  coincidence,  the  pumping  plant  broke  down  at  a  certain 
hour  on  a  certain  day,  and  a  certain  number  of  hours  afterward,  the 
spring  ran  afresh.  That  incident  showed  the  underground  capacity 
of  that  subterranean  gulch,  including  the  capacity  of  the  undergTound 
storage. 

That  formation  was  almost  all  sand  and  gravel.  The  water-table 
in  3  years  of  pumping  was  lowered  from  an  overflow  of  6  or  8  ft. 
above  ground  to  a  ground-water  flow  of  22  ft.  below  the  surface, 
showing  that  the  company  was  pumping  beyond  the  capacity  of  the 
delivery  or  the  water  flow  of  the  country. 

Take  the  other  case,  where  there  is  a  till  flow,  that  is,  in  the 
glacial  deposit  termed  the  till,  where  the  percolation  is  very  slow. 
In  certain  cases  under  the  speaker's  care,  the  flow  of  the  wells  after 
a  rainstorm  was  carefully  timed,  and  the  percolation,  instead  of  being 
immediate,  took  about  2  days.  In  the  case  of  one  large  well,  where 
six  or  seven  holes  had  been  bored  into  the  limestone,  and  where  it 
was  important  to  have  supply  enough  for  the  examination,  careful 
note  was  taken  of  the  times  when  there  was  enough  water  and  when 
the  supply  was  deficient.  Examination  showed  that,  after  a  heavy 
rainstorm,  it  took  2  days  for  this  flow  through  the  till,  that  is,  the 
drift  deposit,  to  get  through  the  rock  and  into  the  wells.  This  shows 
the  extremely  slow  rate  of  percolation. 

There  are  a  great  many  interesting  questions  in  the  whole  region 
about  New  York,  and  it  is  especially  necessary  to  have  known  facts 
tabulated,  as  there  has  been  a  great  deal  of  money  wasted,  especially 
in  developing  what  is  known  as  a  mysterious  underground  supply. 


discussion:  yield  of  underground  reservoirs  221 

In   the   case  previously   cited,   the  wells   were  put   in  for  the  city    Mr. 
under   the    direction    of    a    competent   engineer,    and   the   speaker   re-     ^^''' 
marked  at  the  time  that  he  was  surprised  at  his  being  brave  enough 
to  put  in  such  a  plant  for  that  community.     The  result  has  been  that 
that  city  has  been  compelled  to  buy  up  land  and  territory  after  terri- 
tory to  provide  a  sufficient  underground  supply. 

G.  E.  P.  Smith,*  M.  Am.  Soc.  0.  E.  (by  letter).— The  publication  Mr. 
of  this  scholarly  paper  on  investigations  in  the  Owens  Valley,  and  ™^  ' 
the  studies  and  conclusions  based  thereon,  must  be  welcomed  by  all 
hydraulic  engineers  of  the  arid  West.  In  addition  to  its  immediate 
or  local  value,  the  paper  affords  a  clear  and  concise  exposition  of 
the  general  principles  of  ground-water  storage,  of  recharge  and  loss, 
and  of  the  extent  to  which  ground-waters  can  be  drawn  on  for  munici- 
pal water  supplies,  irrigation,  or  other  purposes.  So  far  as  the  writer 
knows,  it  is  the  first  comprehensive  work  of  its  kind,  and  the  author 
has  the  distinction  of  being  a  true  pioneer  of  the  Profession.  The 
paper  itself  marks  a  new  era  in  the  development  of  ground-water 
studies,  an  era  in  which  scientific  basis  and  logical  methods  supersede 
much  idle  speculation  and  many  misconceptions. 

Too  much  credit  cannot  be  given  to  Mr.  Lee  for  the  thoroughness 
and  application  of  system  displayed  in  his  investigations.  These  fea- 
tures are  exemplified  in  the  excellent  analyses  of  rainfall  distribution, 
of  seepage  losses,  and  of  soil  evaporation  tests.  Where  arbitrary 
factors  have  been  necessitated,  they  have  been  based  on  painstaking 
inspections  and  on  rare  good  judgment.  In  such  cases,  also,  the 
author  was  assisted  by  the  extreme  uniformity  of  natural  conditions 
in  the  Owens  Valley,  especially  of  topography,  valley  fill,  soil  and 
vegetation.  The  application  of  system  in  the  investigational  work 
is  reflected  in  its  orderly  presentation,  and  in  the  use  of  graphical 
methods,  features  which  add  greatly  to  the  value  of  the  paper. 

The  writer's  purpose  is  not  to  criticize,  but  to  broaden  the  foun- 
dation on  which  the  deductions  and  generalizations  of  the  paper  are 
based,  and  to  assist  in  the  extension  of  their  application  to  a  wider 
range  of  climatic  and  geologic  conditions. 

Beginning  in  1906,  the  Arizona  Agricultural  Experiment  Station 
has  carried  on  ground-water  investigations  under  the  writer's  charge 
in  several  valleys  of  southern  Arizona.  These  valleys  vary  greatly 
in  the  degree  of  aridity,  from  the  grassy  sub-arid  Sulphur  Spring 
Valley,  which  is  comparable  to  Owens  Valley,  to  the  severely  arid 
Lower  Gila  Valley.  The  chief  determining  factor  is  the  altitude. 
The  ground-water  hydrology  is  exceedingly  diverse  in  character,  so 
that  it  is  difficult  to  frame  generalizations  that  are  applicable  to  all 
the  valleys. 

*  Tucson,  Ariz. 


223  DISCUSSION :  yield  of  underground  reservoirs 

Mr.  The  most  detailed  study  has  been  that  of  the  valley  of  the  Rillito,* 

^™"'''  a  tributary  of  the  Santa  Cruz,  as  shown  in  Fig.  13.  There  are  striking 
similarities  between  it  and  Owens  Valley.  Both  are  desert  valleys 
in  which  the  surrounding  drainage  is  toward  a  broad,  flat  area,  or 
playa,  and  therefore  they  come  within  the  meaning  of  the  term  "bol- 
son"  or  "semi-bolson",  as  defined  by  Tolman.f  The  Pantano  water- 
shed spills  its  surplus  water  to  the  Rillito;  the  Rillito  delivers  a 
portion  of  its  drainage  to  the  Santa  Cruz,  and  the  Santa  Cruz,  on 
rare  occasions,  has  a  continuous  discharge  to  the  Gila  River.  Exclud- 
ing the  Pantano  bolson  with  its  620  sq.  miles,  the  total  drainage  area 
of  the  Rillito  is  327  sq.  miles,  of  which  56%  is  mountainous  (granitic), 
30%  consists  of  dissected  gravelly  outwash  slopes,  and  14%  is  valley 
land.  The  area  is  nearly  equal  to  that  of  the  Independence  Region, 
though  the  percentage  of  mountain  area  is  higher.  The  lengths  of 
the  valleys  are  the  same — 25  miles — and  both  derive  practically  all 
their  drainage  from  the  right-hand  side.  The  mountain  rainfall,  also, 
is  equal  in  the  two  cases,  varying  from  10  or  12  in.  in  the  foot-hills 
to  30  or  35  in.  at  the  crests. 

The  distinctions  are:  the  Rillito  Valley  lies  at  an  elevation  of 
about  2  400  ft.— considerably  lower  than  Owens  Valley — and  conse- 
•••  quently  the  temperature  is  higher  and  evaporation  is  greater;  the 
mountainous  area  drained  by  the  Rillito  is  on  the  windward  side, 
and  hence  the  rainfall  is  comparatively  high  for  the  region;  the  rain- 
fall-altitude curve  shows  a  continuous  rise  to  the  summit,  at  9  000  ft. ; 
and  there  is  no  perennial  grass  area,  but,  instead,  the  high  mountains 
are  forested  with  pine,  and  the  lower  slopes  and  valley  floor  are  covered 
with  a  diversified  desert  vegetation,  with  mesophytic  trees  along  the 
stream  courses. 

A  survey  of  the  water-table  has  shown  that  the  river  channel  is  not 
coincident  with  the  ground-water  trough;  the  ground-water  on  the 
south  or  left  side  has  a  component  movement  away  from  the  river, 
especially  during  and  after  floods.  The  movement  has  been  studied 
in  lines  of  wells  at  right  angles  to  the  river,  and  the  recharge  which 
occurs  during  a  flood  season  has  been  shown  to  progress  away  from 
the  river  as  a  true  wave.:}:  At  no  point  has  the  water  plane  shown 
any  response  to  direct  precipitation,  the  rainfall  penetrates  only 
a  few  feet  into  the  soil  in  the  most  favorable  years,  and  it  appears 


•  Bulletin  No.  64.  Arizona  Agricultural  Experiment  Station,  1910. 

t  He  states:  "  I  therefore  suggest  that  the  word  be  used  to  coyer  the  watershed  of  a 
centripetal  drainage  system,  including  all  the  area  within  the  limits  of  the  divides.  The 
bolson  may  depart  somewhat  from  a  perfect  topographical  basin  for  evaporation  on  a 
slope  mav  prevent  the  development  of  a  through  drainage,  and  foster  the  centripetal 
variety.  Those  bolsons  whose  surface  water  in  times  of  flood  reaches  some  river  thorough- 
fare some  lower  bolson,  or  the  ocean  direct,  and  consequently  the  playa  portion  ' 
is  poorly  developed  or  lacking,  may  be  called  semi-bolsons  "— Jour/ia?  of  Geology,  X\  11,  No 
■2,  p.  141,  February-March.  1909. 

t  Bulleiin  No.  64,  Arizona  Agricultural  Experiment  Station,  p.  184. 


DISCUSSION  :    YIELD  OF   UNDERGROUND   RESERVOIRS 


223 


atroani  Widths 


Scale,  in  Miles 
10  15  20 


DIAGRAMMATIC  MAP 

OF  SANTA  CRUZ  RIVER,  ARIZONA, 

AND   PRINCIPAL  TRIBUTARIES, 

ILLUSTRATING  THE   REGIMEN 

OF  THE   FLOOD   FLOWS 

AND  OF  THE 

GROUND-WATER  MOVEMENTS. 

NEITHER   SURFACE   WATER 

NOR  UNDERFLOW  IS  CUMULATIVE 


Mr 
Smith. 


^  p 

a. 


Fig.  13. 


32-i  discussion:  yield  of  uxdekground  reservoirs 

Mr.     that  the  recharge  is  due  solely  to  the  seepage  of  the  river  flows  into 
Smith.  ^YyQ  porous  gravels. 

The  structure  of  the  valley  is  of  fundamental  importance.  Fig.  14 
is  a  section  along  the  line,  AA,  the  location  of  which  is  shown  in 
Fig.  13.  The  section  includes  the  mountain  face,  the  Rillito  Valley, 
and  the  smooth  slope  which  separates  the  latter  from  the  Santa  Cruz 
Valley.  The  valley  fill  includes  deposits  of  three  distinct  periods. 
Uppermost  are  the  Recent  deposits  along  the  stream  courses,  laid 
down  by  the  present  system  of  rivers.  The  main  body  of  the  fill,  how- 
ever, is  the  Catalina  Mountain  outwash,  probably  Pleistocene;  and, 
underlying  this  are  older  deposits,  exposed  in  small  outcrops  in  the 
foot-hills.  The  Recent  deposits  include  loose,  coarse,  water-bearing 
gravels;  the  gravels  of  the  outwash  are  for  the  most  part  tightly 
cemented  with  a  secondary  calcareous  deposition  which,  when  present 
in  great  quantity,  is  called  caliche.  As  a  rule,  the  wells  in  the  outwash 
yield  poor  supplies.  Thus  the  Esmond  Well,  in  the  center  of  the 
valley,  southeast  of  Tucson,  which  was  drilled  to  a  depth  of  1  480  ft., 
has  only  3  ft.  of  water-bearing  gravel,  the  rest  of  the  formation  being 
alternating  strata  of  cemented  gravel  and  clay.  Many  wells  in  the 
outwash  yield  practically  nothing,  while  others,  more  fortunately 
situated  with  reference  to  old  stream  beds,  yield  small  supplies  of 
from  50  to  250  gal.  per  min.  The  fact  that  the  first  water-bearing 
stratum  in  the  Recent  fill  yields  good  supplies  has  led  to  the  general 
adoption  of  caisson  well  curbs  built  of  reinforced  concrete,  for  wells 
situated  within  the  area  of  Recent  fill. 

The  interchange  of  water  between  the  Recent  fill  and  the  outwash 
is  difficult  to  estimate,  but,  in  the  aggregate,  it  must  be  quite  extensive. 
The  author  remarks  on  page  151 : 

"Along  the  coast  of  California,  shales  and  cemented  gravels  pre- 
dominate, and  are  practically  non-water-bearing  in  comparison  with 
the  porous  gravels  filling  the  basins." 

Hence,  there  arises  an  ambiguity  with  regard  to  what  shall  con- 
stitute the  basin— the  porous  gravels  only,  or  all  the  fill  within  a 
rock  trough.  The  author  has  used  the  latter  construction  in  his 
work  in  Owens  Valley.  It  is  not  likely  that  close  estimates  can  be 
made  for  the  porous  younger  deposits  alone.  Referring  to  Bulletin  No. 
64  again,  on  page  189  is  the  following: 

"It  may  be  questioned  whether  the  seepage  loss,  if  measured  at 
the  present  time  will  indicate  correctly  the  available  water  supply 
for  pumping.  On  the  one  hand,  present  data  show  a  great  leakage 
from  the  valley,  either  toward  the  south  or  downward  into  the  older 
[Pleistocene]  formation,  and  this  leakage  must  continue  in  the  future. 
•  On  the  other  hand,  the  seepage  loss  of  floods  will  be  greater  if  the 
groundwater  supply  has  been  reduced  by  pumping;  indeed,  it  is  one 
of  the  important  effects  of  pumping  that  the  recharge  of  the  ground- 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS 


225 


K       g      S      ^ 


Elevation,  in  Feet  above  Sea-level. 


Mr. 
Smith. 


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236  discussion:  yield  of  undeegkound  eeservoirs 

Mr.     water  will   be   thus   increased.      At   present   it   may   well  be   assumed 
=mith.  (.}^.jt  these  two  influences  are  balanced." 

The  cementation  described  above  is  a  saving  feature  in  arid  regions, 
since  it  reduces  the  under-drainage  and  holds  the  ground-water  at 
shallower  depths.  In  the  parallel  valleys  west  of  the  Santa  Cruz,  the 
drainage  capacity  exceeds  the  annual  recharge,  with  the  result  that  the 
water-table  lies  at  depths  of  from  200  to  800  ft.,  even  along  portions  of 
the  stream  courses. 

In  estimating  the  annual  recharge  of  the  Eillito  Valley,  the  writer 
made  use  of  the  measured  run-off  from  Sabino  Canyon,  records  for 
which  were  available,  for  the  period,  1904-09.  By  a  comparison  of 
areas  and  altitudes,  and  of  simultaneous  gaugings  at  the  mouths 
of  canyons,  the  run-off  for  the  other  tributaries  was  estimated.  Meas- 
urements of  seepage  loss  were  the  next  need.  For  moderate  floods, 
the  problem  was,  not  the  percentage  of  loss,  it  being  total,  but  the 
quantity  and  location  of  the  loss.  Logs  of  wells  revealed  the  extent 
of  the  storage  capacity.  With  the  foregoing  data  the  recharge  for 
a  distance  of  12  miles  was  estimated  at  23  000  acre-ft.  per  year.  It 
is  hardly  necessary  to  disavow  any  high  degree  of  accuracy,  but,  even 
though  the  probable  error  is  20%,  such  estimates  are  highly  useful. 

Transpiration. 

In  the  Owens  Valley  experiments,  the  evaporation  from  the  soil 
and  transpiration  from  the  salt  grass  were  treated  together,  and  a 
straight-line  relationship  was  established  between  the  water  loss  and 
the  depth  of  the  water-table  below  the  ground  surface.  It  is  worthy 
of  note  that  the  loss  of  ground-water  from  the  salt  grass  in  the  3-ft. 
zone  was  sufficient  for  the  irrigation  of  an  equally  large  area  of  alfaKa, 
and  the  loss,  where  the  depth  to  water  was  4  ft.,  was  sufficient  for 
the  irrigation  of  most  other  crops. 

If  two  additional  tank  sets  had  been  provided,  and  maintained 
without  grass,  one  with  water  level  at  a  depth  of  2  ft.  and  one  with 
depth  of  4  ft.,  and  thus  used  as  check  tanks,  it  would  have  been 
possible  to  differentiate  between  the  combined  effect  of  evaporation 
and  transpiration  and  the  effect  of  evaporation  alone.  The  evidence 
of  the  data  presented  indicates  that  the  combined  loss  is  approximately 
twice  the  loss  due  to  evaporation  from  the  soil.  For  it  is  to  be  noted 
from  Fig.  10  that  the  loss-depth  line  in  summer  approaches  closely 
to  the  summer  loss  from  a  free  water  surface,  while  in  winter  the  loss- 
depth  line  falls  short  of  the  corresponding  free-water  loss  about  one- 
half.  Although  the  estimated  summer  transpiration  loss  from  alfalfa 
is  87%  of  the  free-water  loss,  yet  the  transpiration  from  salt  grass 
must  be  much  less  than  that  from  alfalfa,  because  of  the  smaller 
leaf  surface  exposed,  and  the  direct  evaporation  from  the  soil  must 
be  greater  than  in  the  case  of  alfalfa. 


discussion:  yield  of  underground  reservoirs  227 

In  southern  Arizona  and  contiguous  areas,  the  normal  desert  Mr. 
valley  has  no  extensive  flat  shallow-water  district  like  that  of  Owens  '"^ 
Valley.  The  water  plane  is  usually  at  a  depth  exceeding  15  ft.,  and 
is  thus  beyond  the  influence  of  capillary  action.  In  some  cases  there 
ate  small  cienegas,  covering  an  acre,  more  or  less,  and  in  the  Sulphur 
Spring  and  San  Simon  Valleys  there  are  playas  of  considerable  extent; 
but  many  valleys  of  this  region  have  modified  river  drainage  systems, 
with  bottom-lands  carrying  a  surprising  quantity  of  vegetation, 
usually  trees  and  shrubs. 

Formerly,  the  river  channels  were  poorly  developed  or  entirely 
lacking,  and  the  occasional  floods  spread  out  over  the  bottom-lands  and 
supported  a  growth  of  sacaton  and  other  grasses;  but,  with  the  coming 
of  the  white  man,  with  his  herds  of  cattle,  and  the  overstocking  of 
the  ranges  in  the  Eighties,  great  areas  were  denuded  of  grass,  and 
the  concentrated  flood-waters  soon  cut  wide  channels  through  the  loam 
and  adobe  down  to  a  gravelly  bottom.  Following  the  change  in  the 
character  of  the  run-off,  the  sacaton  disappeared,  and  trees,  notably 
mesquite,  took  possession.  Where  the  depth  to  ground-water  is  within 
25  or  30  ft.,  the  trees  have  become  continuous  forests  covering  the 
ground.  That  the  trees  send  their  roots  down  to  the  water-table  is 
easily  proven,  for  the  caving  banks  of  rivers  and  arroyas  reveal  them. 
The  mesquite,  in  particular,  has  deep,  strong,  tap-roots,  with  a  gen- 
erous development  of  feeders. 

The  hypothesis  has  been  held  by  the  writer  for  a  long  time  that 
the  water  drawn  up  through  trees  and  transpired  constitutes  the  ' 
principal  loss  from  the  ground-water  reservoir,  and  that,  in  some  cases, 
this  loss  is  the  total  loss,  while  in  all  cases  evaporation  is  an  agency 
of  less  import.  This  paper  tends  to  confirm  the  hypothesis.  The  author 
states,  however,  concerning  the  processes  of  soil  evaporation,  transpira- 
tion, and  stream  flow,  that  "with  the  exception  of  transpiration  from 
trees",  they  "are  now  capable  of  measurement  with  relative  accuracy 
at  reasonable  cost."  In  order  to  apply  the  principles  which  he  has 
so  ably  developed  to  the  regions  somewhat  more  arid  than  Owens 
Valley,  it  is  essential  to  learn  much  more  than  is  now  known  about 
tree  transpiration. 

Botanical  literature  offers  little  assistance  in  this  problem.  The 
single  experiment  or  estimate  which  is  found  in  all  botanical  text- 
books is  that  in  Austria  a  high  beechwood  forest  transpires  30  000  liters 
daily  per  hectare  during  the  growing  season  of  6  months.  This  is 
equivalent  to  22  in.  depth  of  water  over  the  land.  It  is  stated,  further, 
that  from  250  to  500  grammes  of  water  are  transpired  for  every  gramme 
of  dry  solid  matter  produced. 

Mr.  Lee  says  of  transpiration  that  it  "differs  in  different  species  of 
plants,"  and  "King's  experiments  indicate  that  humidity  does  not 
affect  transpiration.     For  a  species  growing  in  a  definite  locality,  light 


238  discussion:  yield  of  undergkound  reservoirs 

Mr.  and  available  soil  moisture  are  the  controlling  factors."  These  state- 
Smith,  j^gjjj-g  are  surely  open  to  question,  as  will  be  explained  presently. 
It  is  probable  that  all  plants  tend  toward  the  same  rate  of  relative 
transpiration  per  unit  of  surface  exposed,  and  the  principle  is  well 
established  that  humidity  is  a  potent  factor  of  transpiration,  as  well 
as  are  light  and  soil  moisture.  The  significance  of  these  corrections 
lies  in  the  fact  that  ground-water  reservoirs  are  of  chief  importance 
in  arid  regions;  and  in  such  regions,  with  low  humidity,  brilliant  light, 
and  high  rates  of  transpiration,  even  the  xerophytic,  or  drouth-resistant, 
plants,  under  certain  conditions,  become  most  profligate  in  dissipating 
the  only  available  water  resources. 

Recent  researches  of  the  Desert  Botanical  Laboratory  of  the  Car- 
negie Institution  have  brought  out  some  pertinent  new  principles  of 
transpiration.  The  work  of  F.  Shreve  in  the  tropical  mountain  rain- 
forest of  Jamaica  has  yielded  the  conclusions  that  humidity  is  a 
factor  of  much  influence,  and  that  transpiration  is  approximately 
proportional  to  evaporation.     He  says:* 

"Although  high  humidities  (90  to  95  per  cent.)  have  been  found 
to  reduce  the  absolute  rate  of  transpiration  below  its  amount  at  rela- 
tively low  humidities  (55  to  71  per  cent,),  as  is  to  be  expected,  the  rate 
of  relative  transpiration  continued  to  be  of  the  same  general  order  of 
magnitude  at  all  humidities  which  are  well  above  the  minimal  point 
for  rain-forest  plants." 

Relative  transpiration  is  a  term  used  to  define  the  ratio  of  trans- 
piration to  evaporation.  Further,  Shreve  has  studied  data  obtained 
by  him  in  Jamaica,  in  comparison  with  similar  investigations  car- 
ried on  at  Tucson,  by  B.  E.  Livingston  on  several  desert  ephemerals, 
and  by  Edith  B.  Shreve  with  the  palo  verde,  Parhinsonia,  which  is 
rated  as  "a  most  successful  desert  tree".     To  quote  again  :f 

"A  general  review  of  the  data  under  comparison  indicates  that, 
in  spite  of  minor  diiierences,  there  is  a  greater  uniformity  among 
the  relative  transpiration  maxima  for  the  rain-forest  and  for  the 
desert  than  might  be  expected.  When  such  a  uniformity  is  considered 
in  the  light  of  the  fact  that  the  evaporation  is  very  many  times  greater 
in  the  Arizona  desert  than  in  the  Jamaican  rain-forest,  it  forces  the 
conclusion  that  the  transpiration-rates  in  the  plants  of  the  two  regions 
must  be  roughly  proportional  to  the  evaporation-rates,  else  the  relative 
transpiration-rates  would  not  remain  so  nearly  equal.  _  In^  short,  it  is 
the  desert  plants  in  which  the  rate  of  transpiration  is  high  and  the 
rain-forest  plants  in  which  it  is  low,  which  is  quite  the  reverse  of 
the  commonly  accepted  view." 

G.  F.  Freeman,  plant  breeder  of  the  Arizona  Agricultural  Experi- 
ment Station,  has  made  simultaneous  tests  of  transpiration  on  a  peach 
tree  and  a  creosote  bush  growing  in  close  proximity.     He  found  a  very 


*  '■  Year  Book  No.  12,"  Carnegie  lastitution  of  Washington,  1913,  p.  74. 
■\Ibid.,  pp.  75-76. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS  229 

slightly   higher   transpiration-rate   for   the   peach    tree   per   pound    of    Mr 
green  matter,  but,  when  based  on  the  area  of  leaf  surface,  the  rate  ' 
for    the    creosote    bush    was    in    excess.*      The    creosote    bush    is    an 
extremely  xerophytic  plant,  and  forms  the  principal  vegetation  of  the 
dryest  slopes. 

The  establishment  of  the  principle  of  equal  relative  transpiration- 
rates  makes  it  possible  to  eliminate  from  many  discussions  factors 
such  as  light,  air  pressure,  temperature,  and  humidity,  and  to  base  esti- 
mates of  transpiration  on  the  more  easily  measured  evaporation  from 
a  free  water  surface.  Also,  the  principle  harmonizes  the  author's 
estimate  of  annual  transpiration  loss  from  alfalfa  with  King's  estimate 
for  clover  in  Wisconsin.  The  leaf  characteristics  of  the  two  crops 
are  very  similar.  The  estimate  for  alfalfa  is  41  in.  depth  of  water 
transpired  through  the  plants  and  10  in.  additional  evaporated  from 
the  soil;  for  clover  the  estimate  is  22.3  in.  for  both  processes  combined. 
The  rates  of  evaporation  in  Owens  Valley  and  in  Wisconsin,  however, 
are  approximately  as  2  to  l.f  Since  the  rates  for  southern  Arizona  and 
for  Wisconsin  are  as  2i  to  1,  the  inference  can  be  drawn  that,  in 
Arizona  it  requires  about  56  in.  for  the  proper  irrigation  of  alfalfa. 

Before  condemning  all  desert  vegetation  indiscriminately,  however, 
an  ameliorating  factor  must  be  taken  into  consideration.  Desert 
plants  possess  many  queer  habits  by  which  they  protect  themselves 
from  the  tendency  toward  high  transpiration-rates.  On  hot  dry  days 
they  close  their  stomatal  openings.  In  times  of  drouth  they  drop  their 
leaves.  The  leaves  are  invariably  small.  The  leaves  of  many  species 
are  covered  with  hairs.  Some  of  the  cacti  are  provided  with  water 
storage  organs  either  in  the  roots  or  in  the  stems.  Hence,  plants 
pass  successfully  through  seasons  when  the  soil  moisture  around  their 
roots  becomes  as  low  as  4  per  cent.  This  power  of  self-protection  is 
vital  to  the  vegetation  of  the  outwash  slopes  (usually  but  improperly 
called  mesas),  where  the  depth  to  the  water  level  ranges  sometimes 
as  great  as  600  ft.  There  is  no  evidence,  however,  that  the  power  is 
exercised  by  trees  growing  on  the  bottom-lands,  where  the  roots  are 
bountifully  supplied  from  below  the  ground-water  table,  or  by  alfalfa 
and  other  field  crops,  so  long  as  they  are  well  irrigated. 

Adopting  now  the  principle  that  transpiration  varies  as  evapora- 
tion, soil  moisture  conditions  being  assumed  to  be  uniform,  the  trans- 
piration-rate for  the  beechwood  forest  previously  quoted  must  be  multi- 
plied by  24  to  obtain  the  rate  for  arid  regions.  The  result  is  55  in. 
depth  of  water  per  annum,  a  quantity  that  probably  represents  fairly 
well  the  transpiration  loss  from  the  Cottonwood  trees  which  fringe 
the  rivers  for  miles  and  are  abundant  usually  on  the  upper  courses 
of  the  tributaries.     The  loss  from  mesquite  forest,  on  account  of  the 


♦Unpublished  work. 

tSee  new  Evaporation  Chart,  "The  Plant  World,"  Vol.  XIV,  No.  9, 1911,  p.  219. 


230         DISCUSSION :  yield  of  underground  reservoirs 

Mr.     smaller  leaf  expanse,  is  perhaps  one-half  as  great  as  that  from  cotton- 
S""'^^-  wood  trees. 

As  a  corollary  to  the  foregoing  discussion,  it  is  clear  that  the  duty 
of  water  to  be  provided  for  in  any  locality  is  proportional  to  the 
evaporation-rate.  On  this  basis,  the  high  duty  of  water  maintained 
in  the  San  Bernardino  Valley,  in  southern  California,  7  or  8  acres 
per  miner's  inch,  is  no  more  creditable  than  the  duty  in  Salt  River 
Valley,  Arizona.,  where  for  the  last  3  years,  the  average  duty  of 
water,  delivered,  has  been  5.4  acres  per  miner's  inch.  Following  the 
over-use  of  water  in  many  localities  where  it  is  abundant,  some  irri- 
gationists  now  go  to  the  other  extreme,  and  advocate  an  impossibly 
high  duty  in  the  most  desert  valleys.  Investigations  relating  to  duty 
of  water  should  be  accompanied  always  by  current  observations  of 
the  evaporation  rate,  so  that  the  results,  when  published,  may  be  of 
more  than  local  value.  This  precaution  for  making  the  investigations 
of  wide  interest  has  seldom  been  exercised. 

A  Principle  of  Ground- Water  Hydrology. 

I  That  the  ground-waters  in  arid  valleys  are  not  cumulative,  is  a 
\  principle  which  needs  additional  emphasis.  Although  there  is  a  con- 
-'  tinuous  movement  of  ground-water  longitudinally  in  a  valley,  yet, 
in  the  main,  the  ground-water  of  one  region  does  not  get  down  into  the 
next  region.  In  this  respect  there  is  a  close  analogy  between  surface 
flows  and  underflows.  Fig.  13  is  a  diagrammatic  map  of  the  Santa 
Cruz  River  and  its  principal  tributaries.  The  widths  of  the  lines  are 
roughly  proportional  to  the  widths  of  the  river  channels,  and  indicate 
the  regimen  of  the  floods — the  narrow  torrents  of  the  mountain  can- 
yons, and  the  spreading  out  over  sandy  beds  and  rapid  absorption  by 
percolation  after  leaving  the  canyon  mouths.  Normally,  the  river 
beds  are  dry.  Many  floods  of  the  head-waters  do  not  reach  Calabasas, 
and  few  floods  which  pass  Calabasas  reach  Tucson.  The  river  is  ever 
a  dwindling  stream,  and,  though  draining  greater  areas,  brings  less 
water  and  smaller  floods  to  the  junctions  with  some  of  its  tributaries 
than  do  those  tributaries.  Finally,  at  a  point  about  10  miles  beyond 
the  limit  of  the  map,  the  channel  is  narrowed  down  to  a  width  of 
12  ft.,  and  2  miles  farther  on  it  entirely  fades  out.  Likewise,  the 
ground-water  movements  are  represented  by  the  same  map.  These 
movements  are  most  active  where  the  river  beds  are  widest,  where  the 
recharging  occurs;  but  at  all  points  along  the  stream  courses  the 
moving  ground-water  is  sustaining  a  loss,  due  mostly  to  transpiration, 
and  the  loss  in  any  region  is  commensurate  to  the  recharge  in  that 
region.  The  factors  of  recharge,  loss,  and  forward  movement  are 
closely  interrelated,  though  of  varying  importance  in  different  locali- 
ties within  a  region  in  their  effects  on  the  ground-water  supply. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS  231 

A  logical  sequence  of  these  conditions  is  that  extensive  concentrated  Mr. 
ground-water  development  is  impossible.  Vast  areas  of  fertile  land  ™  ' 
that  could  be  reached  easily  by  canals  will  ever  remain  desolate,  but 
there  are  hundreds  of  small  areas,  usually  stretching  along  the  river 
courses,  capable  of  reclamation  by  the  utilization  of  ground-waters. 
The  best  of  these  small  projects  are  to  be  found  farther  up  stream. 
"The  mountain  water  will  not  come  down  into  the  desert  very  far; 
we  must  go  toward  the  mountain.  The  water  must  be  used  as  near 
as  possible  to  its  source."* 

Another  sequence  of  the  foregoing  principle  is  that  new  diversions 
of  ground-water  in  arid  valleys  are  not  so  prejudicial  to  older  rights  as 
has  been  assumed  oftentimes,  and  the  doctrine  of  priority  now  applied 
to  underflow  streams  of  a  definite  character  needs  modification.  In  a 
discussion  of  the  application  of  the  doctrine  to  underflow  gravity 
ditches,f  the  writer  has  suggested  four  points  of  limitation.  They 
might  well  be  applied  to  pumping  operations  also.  The  limitations 
relate  to  the  burden  of  proof,  to  the  extent  of  the  injury,  to  co-opera- 
tion in  development  work,  and  to  the  efficiency  of  the  collecting 
agencies.  Another  consideration  is  that  active  interference  between 
underflow  ditches  or  between  wells  does  not  begin  at  once,  but  may 
require  many  months  of  lowering  water  plane,  and,  before  the  time 
has  elapsed,  one  big  flood  may  refill  the  gravels,  whereupon  all  effects 
of  the  previous  drafts  on  the  ground-water  supply  are  obliterated. 

Estimates  of  Safe  Yield. 

The  large  items  of  the  author's  estimates  carry  much  conviction 
as  to  their  accuracy.  Some  of  the  small  items,  however,  possibly 
need  additional  study. 

1. — Percolation  from  Precipitation  on  Intermediate  Mountain 
Slopes. — The  Sierra  slopes  are  said  to  be  of  unfissured  granite  covered 
by  a  mantle  of  loose  rock.  Table  16  gives  the  average  annual  rainfall 
as  12  to  20  in.,  derived  mainly  from  the  slow  rains  and  snows  of 
winter.  Similar  conditions  exist  on  the  slopes  of  the  Catalina  and 
Rincon  Mountains,  near  Tucson,  but  observation  indicates  that  most 
of  the  precipitation  is  absorbed  by  the  porous  overburden,  wherein 
it  supports  an  extensive  desert  vegetation.  There  is,  of  course,  a  slow 
creeping  of  the  water  downward  at  times,  but  very  little  of  it  reaches 
the  valley.  There  are  springs  at  the  base  of  the  slopes,  but  they  are 
small,  more  suitable  to  be  measured  in  cattle  drinks  than  in  second- 
feet.  The  run-off  factors  used  for  the  intermediate  mountain  slopes 
of  Owens  Valley  appear  to  be  too  high. 

2. — The  Upper  Seeley  Spring. — The  location  of  this  spring,  at  the 
north  base  of  Charlies  Butte,  raises  a  question  as  to  the  derivation  of 

*  Proceedings,  16tti  National  Irrigation  Congress,  1908,  p.  206. 

t  22d  Annual  Report,  Arizona  Agricultural  Experiment  Station,  1911,  p.  570. 


232         discussion:  yield  of  underground  reservoirs 

Mr.     its  water.     If  it  is  lateral  flow  from  the  outwash  slopes,  it  is  included 

Smith,  rightly    in   the   summary   of   ground-water   losses,   but    if    it    is   river 

underflow  brought  to  the  surface  by  the  intervention  of  the  butte — 

a    hydrologic    condition    of    common    occurrence    in    the    Southwest — 

then  it  should  be  omitted  from  consideration. 

S. — It  is  stated  that  on  the  outskirts  of  the  salt  grass  there  is 
a  strip  of  greasewood  and  bunch  grass,  that  bordering  this  there  is 
another  zone  of  luxuriant  sagebrush,  and  that  the  depth  to  water 
beneath  these  areas  is  from  8  to  20  ft.  In  the  light  of  the  foregoing 
discussion  on  transpiration,  it  is  evident  that  the  water  loss  from  these 
bordering  zones  is  of  so  much  importance  that  an  effort  should  be 
made  to  measure  or  estimate  it. 

4 — Another  question  of  doubt  to  the  writer  is  whether  the  underflow 
at  Alabama  Hills  can  be  disregarded.  The  river  bottoms  here  are  3 
miles  wide,  and  the  rock  trough  is  shown  to  be  at  least  832  ft.  deep. 
The  slope  of  the  water-table  is  8  ft.  per  mile.  Although  the  valley 
fill  on  the  Inyo  Mountain  side  is  composed  of  fine  sand,  yet  on  the 
opposite  side  there  may  be  strata  of  good  water-bearing  gravels 
deposited  by  living  rivers  from  the  Sierra  Range.  A  forward  move- 
ment of  the  underflow  of  6  in.  a  day  throughout  the  section  implies 
an  item  of  loss  of  more  than  20  sec-ft.  This  problem  gives  the  writer 
more  concern  because  in  the  arid  Arizona  valleys  the  bottom-lands  do 
have  usually  some  good  water-bearing  gravels.  Thus,  in  the  Santa 
Cruz  "narrows",  opposite  Sentinel  Hill,  at  Tucson,  the  underflow  in 
the  first  water  stratum  must  have  been  at  least  10  sec-ft.  before  the 
recent  development  was  made.  The  underflow  loss  can  be  measured 
or  estimated  by  the  Slichter  method,  and  should  be  included  in  the 
balance  sheet.  Perhaps  a  fair  estimate  for  Owens  Valley  is  that  the 
underflow  gain  at  the  north  end  of  the  Independence  Eegion  equals 
the  underflow  loss  at  the  Alabama  Hills. 

In  contrast  with  the  author's  orderly  estimates  are  the  crude 
methods  which  have  found  favor  heretofore.  A  recent  report  on 
ground-water  resources  in  an  Arizona  valley  is  based  on  absurd  hypoth- 
eses, yet,  on  account  of  its  authorship,  the  report  ought  to  have  been 
final  and  conclusive.  The  report  first  recites  the  water-shed  area 
and  rainfall,  then  applies  Newell's  run-off  curves  (which  give  values 
too  high  for  arid  regions),  then  deducts  surface  run-off,  the  quantity 
already  applied  to  irrigation,  and  an  allowance  for  evaporation  from 
the  dry  river  bed,  and  asserts  that  the  remainder  is  underflow  at  the 
given  cross-section  of  the  valley.  It  ignores  the  largest  factor  of 
ground-water  loss — transpiration — and  assumes  that  the  underflow  is 
cumulative  from  the  sources  of  the  stream  to  the  place  under  con- 
sideration. The  magnitude  of  the  underflow  thus  computed  is  exces- 
sively high,  and  is  calculated  to  invite  unwarranted  expenditures  in 
development. 


DISCUSSION  :    YIELD   OF   UNDERGROUND  RESERVOIRS  233 

On  page  153  is  the  statement:  Mr. 

Smith. 

"There  are  *  *  *  two  possible  methods  of  measuring  the  rate 
of  recharge,  either  by  determining  the  total  percolation  from  various 
sources  into  the  porous  material  of  the  basin,  or  by  determining  the 
ground-water  losses." 

The  latter  method  is  applicable  in  valleys  where  the  loss  areas  are 
fairly  compact  and  the  vegetation  fairly  uniform;  but,  with  a  native 
vegetation  of  trees  and  shrubs,  diverse  in  leaf  expanse,  in  height,  and 
in  stand,  and  extending  over  irregular  areas,  there  is  little  hope 
of  approximating  reliable  estimates.  On  the  other  hand,  as  the 
recharge  in  very  arid  valleys  is  practically  all  from  stream  flows, 
the  first  method  promises  more  accurate  quantitative  results.  The 
essential  features  of  the  first  method  are  an  area  survey  and  some 
gauging  stations  carefully  selected,  at  the  mouths  of  representative 
canyons,  at  the  mouths  of  representative  washes  draining  the  outwash 
slopes,  and  near  the  outlet  of  the  region.  Fluctuations  in  wells,  and 
water  contour  maps,  present  excellent  qualitative  studies,  inasmuch 
as  they  reveal  the  direction  of  ground-water  movements,  the  localities 
of  active  recharge,  and  the  areas  of  loss.  The  first  method  has  the 
disadvantage  of  requiring  more  attention  to  the  residual  losses  in 
determining  the  safe  yield  than  does  the  second. 

The  author  has  not  discussed  the  probable  variations  in  safe  yield 
from  year  to  year,  though  this  is  of  great  importance.  Unfortunately, 
years  of  high  rainfall,  and  again  lean  years,  come  in  long  series  with 
great  perversity.  Rainfall  records  at  Tucson  show  6  years,  from  1899 
to  1904,  with  less  than  10  in.  of  rain  each  year,  followed  by  5  good 
years  with  more  than  10  in.  each  year,  since  which  time  there  have 
been  4  years  with  rainfall  below  the  average.  The  discharge  from 
Sabino  Canyon  has  varied  from  2  900  to  46100  acre-ft.  per  year. 
Ground-water  levels  respond  more  or  less  quickly  to  the  variations  in 
rainfall,  and  in  some  localities  fluctuate  over  a  wide  range.  Thus, 
along  a  section  of  Pinal  Creek,  the  water-table  has  been  as  high  as 
12  ft,  and  as  low  as  85  ft.  from  the  surface.  The  recent  introduction  of 
pump  irrigation  along  the  creek  will  increase  the  range  of  fluctuation. 
Investigations  of  safe  yield  are  most  fortunate  if  made  during  a 
period  when  the  rainfall  is  normal.  In  any  case,  the  investigations 
should  extend  over  several  years,  so  as  to  eliminate  the  effects  of 
storage  from  year  to  year.  If  data  on  the  position  of  the  water-table 
at  many  places  can  be  secured  during  the  year  for  which  the  estimates 
are  make,  the  increase  or  decrease  in  the  storage  supply  can  be  com- 
puted, and  should  appear  as  one  item  in  the  balance  sheet. 

Ground-water  reservoirs  of  large  capacity  are  better  equalizers  of 
the  water  supply  than  are  surface  reservoirs,  but  those  of  small 
capacity  may  be  poor  equalizers.  In  nearly  all  cases  the  highest  utiliza- 
tion   of    ground-water    requires    the    recognition    of    the    principle    of 


234         DISCUSSION :  yield  of  underground  reservoirs 

Mr.     fluctuating  area   under  cultivation.     Farmers  are  loath  to   admit  the 
Smith.  jjg(.gggity  for  fluctuating  area ;  the  principle  is  not  ideal,  but  in  time 
it  will  be  adopted  by  Courts  and  otherwise. 

The  author's  summary  of  residual  losses  applies  to  many  valleys 
perfectly.  The  outlet  loss  is  not  a  loss  to  the  State,  however,  inasmuch 
as  it  becomes  available  in  the  next  valley  region.  What  is  termed 
the  Artesian  loss  is,  in  many  cases,  not  truly  Artesian  in  char- 
acter. This  loss  and  the  springs'  loss  are  preventable  by  pumping 
operations.  The  loss  by  transpiration  through  trees  is  preventable, 
also,  inasmuch  as  the  feasible  pumping  lift  is  much  greater  than 
the  limit  of  penetration  of  tree  roots.  Developments  of  the  last 
3  years  in  pumping  machinery  have  doubled  the  economical  limit 
for  depth  of  pumping.  Defining  the  efficiency  of  ground-water  reser- 
voirs as  the  ratio  of  the  quantity  recovered  for  irrigation  to  the  total 
recharge,  it  is  fair  to  anticipate,  and  to  design  works  for,  an  exceed- 
ingly high  efficiency,  higher  than  many  surface  reservoirs,  which  lose 
from  3  to  10%  through  evaporation  and  an  equal  quantity  through 
losses  from  a  long  supply  canal. 

Methods  of  increasing  the  safe  yield  require  some  variation  from 
those  proposed,  in  order  to  make  them  applicable  to  conditions  in 
very  arid  valleys.  Efforts  to  bring  about  greater  absorption  of  flood- 
waters  are  not  needed.  The  floods  are  wholly  absorbed  now,  except 
for  an  occasional  season  of  high  rainfall,  occurring  perhaps  once  in 
15  years.  The  efficiency  of  absorption  through  stream  beds  must  be 
higher  than  that  of  absorption  on  an  exposed  slope.  The  only  prom- 
ising method  is  the  elimination  of  transpiration  through  the  denuda- 
tion of  the  bottom-lands.  The  native  forests  and  scattered  trees  should 
be  removed,  and,  so  far  as  the  water  supply  permits,  replaced  by 
vegetation  that  is  useful  to  man. 

In  conclusion,  the  investigations  in  Owens  Valley  are  timely,  for 
the  extensive  development  of  ground-waters  in  the  Southwest  points 
already  to  the  over-draft,  and  in  some  places  to  the  exhaustion,  of  the 
supply  within  a  few  years.  The  Engineering  Profession,  and  not  the 
Courts  of  Law,  should  take  the  prominent  part  in  the  final  adjustment 
of  pumping  operations  to  the  limiting  physical  conditions. 
Mr.  O.    E.    Meinzer,    Esq.*    (by    letter).— Mr.    Lee's    investigation    in 

Meinzer.  q^^^^  Valley  is  a  valuable  contribution  to  the  study  of  ground-water. 
The  demand  for  irrigation  supplies  and  the  increasing  availability  of 
ground-water  because  of  improved  irrigation  and  cultural  methods  and 
decreased  pumping  costs  have  created  a  need  for  information  as  to 
the  magnitude  of  ground-water  supplies,  the  question  being  primarily 
not  as  to  the  quantity  stored  in  the  earth  but  as  to  the  annual  recharge 
or  safe  yield.     Any  contribution  to  the  methods  for  estimating  the 

*  In  Charge,  Ground- Water  Div.,  Water  Resources  Branch,  U.  S.  Geological  Survey, 
Washington,  I).  C. 


discussion:  yield  of  underground  reservoirs  235 

annual  supplies  of  ground-water,  therefore,  is  especially  valuable  at  Mr. 
this  time.  Four  principal  methods  or  groups  of  methods,  which  may 
be  called  the  percolation,  underflow,  water-level,  and  evaporation 
methods,  have  been  used.  The  first  consists  in  estimating  the  quantity 
of  water  that  percolates  into  an  underground  reservoir  from  streams 
or  other  surface  sources;  the  second  in  measuring  the  flow  of  ground- 
water at  selected  cross-sections,  being  similar  in  principle  to  the  gauging 
of  surface  streams;  the  third  in  observing  fluctuations  in  the  water- 
table,  which  represent  filling  or  emptying  of  the  underground  reser- 
voir; and  the  fourth  in  measuring  the  discharge  of  ground-water 
through  evaporation  from  soil  and  plants.  All  these  methods  are 
laborious  and  difficult  to  apply,  and  none  of  them  can  be  expected  to 
produce  precise  results,  but  they  are  valuable,  nevertheless,  because 
they  give  some  tangible  basis  for  estimating  ground-water  supplies. 
In  the  Owens  Valley  investigation,  Mr.  Lee  used  both  percolation  and 
evaporation  methods,  his  distinctive  contribution  consisting  in  devel- 
oping the  latter  method  and  placing  it  on  a  quantitative  basis. 

The  evaporation  method  gives  promise  of  extensive  applicability 
because  a  large  number  of  the  ground-water  reservoirs  that  will  be 
developed  for  irrigation  discharge  wholly  or  chiefly  by  evaporation. 
Debris-filled  basins  are  the  most  characteristic  features  of  the  United 
States  west  of  the  Rocky  Mountains.  They  are  of  two  types:  Those 
which  discharge  ground-water  through  springs  and  evaporation  areas, 
as  described  by  Mr.  Lee,  and  those  which  do  not.  In  the  geologic 
literature  dealing  with  these  basins  this  fundamental  distinction  is 
generally  ignored,  and  the  characteristics  of  the  evaporation  areas  are 
commonly  accounted  for  by  the  wholly  inadequate  explanation  of  evapo- 
ration of  surface  waters.  The  process  of  ground-water  evaporation, 
however,  has  been  clearly  stated  by  F.  H.  Newell,*  M.  Am.  Soc.  C.  E., 
in  one  of  the  earliest  papers  on  water  resources  published  by  the  United 
States  Geological  Survey,  and  in  recent  ground-water  investigations  the 
significance  of  evaporation  areas  has  come  to  be  clearly  recognized, 
Mr.  Lee  has  furnished  experimental  data  showing  that  these  areas  are 
quantitatively  important  in  discharging  ground-water. 

Work  in  numerous  debris-filled  basins  has  shown  that  it  is  entirely 
feasible  to  ascertain  from  surface  indications  whether  or  not  a  basin 
is  discharging  ground-water  by  evaporation.  The  evaporation  areas 
in  some  of  the  basins  have  been  mapped  with  nearly  the  same  accuracy 
that  is  possible  in  mapping  geologic  formations.  The  three  criteria, 
all  of  which  are  suggested  in  the  paper,  are  (1)  moisture  of  the  soil; 
(2)  soluble  salts  at  the  surface;  and  (3)  native  plants  that  feed  on 
ground-water.  Experience  is  necessary,  of  course,  for  a  proper  appli- 
cation of  these  criteria,  but  they  are  trustworthy  when  rightly  used. 
Moreover,  they  can  be  tested  at  any  time  by  making  a  shallow  boring, 
*  "  Water  Supply  for  Irrigation,"  U.  S.  Geol.  Survey,  13th  Annual  Rept.,  1893.    Pt.  3,  p.  29. 


236  discussion:  yield  of  undekgeound  reservoirs 

Mr.  for  ground-water  evaporation  takes  place  only  where  the  water-table 
Meinzer.  ^^  ^^^^^  ^-^^  Surface.  In  a  recent  ground-water  survey  of  the  Big 
Smoky  Valley,  Nevada,  the  relations  between  the  vegetation  zones  and 
the  depth  to  the  water-table  were  found  to  be  very  similar  to  those 
stated  by  Mr.  Lee  (page  198),  but  the  plant  species  that  serve  as 
indicators  of  ground-water  are  not  the  same  in  different  parts  of 
the  West.  The  mapping  of  evaporation  areas  is  important,  not  only 
because  these  areas  make  possible  estimates  of  the  annual  supplies, 
but  also  because  they  reveal  the  base  level  of  the  ground-water  surface, 
and  thus  make  possible  a  forecast  of  the  depth  to  water  in  other  parts 
of  the  basins  in  which  they  occur. 

Mr.  Lee's  first  conclusion  (page  149)  is  open  to  criticism  in  being 
too  general.  On  the  basis  of  his  investigation  in  the  Owens  Valley, 
he  concludes  that  the  underground  reservoirs  of  California  and  the 
Southwest  are  water-tight  rock  basins.  Many  of  the  debris-filled  basins 
of  the  Southwest,  however,  even  those  comparatively  well  enclosed  by 
mountains,  have  no  ground-water  discharge  through  springs,  evapora- 
tion, or  transpiration,  and  it  must  be  assumed  that  the  supplies  which 
they  undoubtedly  receive  are  disposed  of  entirely  through  rock  absorp- 
tion or  underground  channels  of  escape.  Some  of  the  reservoirs  which 
discharge  water  by  springs,  soil  evaporation,  and  transpiration,  no 
doubt  also  suffer  losses  through  rock  absorption  or  leakage.  In  this 
respect  each  basin  forms  a  separate  problem,  the  amount  of  under- 
ground loss  depending  on  the  stratigraphy  and  structure  as  well  as 
the  topography.  It  should  be  noted  that  such  loss,  if  heavy,  will  make  the 
estimates  obtained  by  the  percolation  method  too  large  and  may  make 
those  obtained  by  the  evaporation  method  too  small.  One  of  the  sources 
of  the  public  supply  of  Goldfield,  Nev.,  has  consisted  of  wells  in  a 
closed  debris-filled  basin  which  has  no  discharge  by  evaporation.  Such 
a  basin  will  yield  some  water  even  though  it  has  no  natural  discharge 
through  springs,  evaporation,  and  transpiration,  but  its  yield  will 
be  less  than  the  quantity  that  percolates  from  surface  sources  to  the 
water-table. 

The  writer  was  disappointed  in  not  finding  in  Mr.  Lee's  paper  a  more 
definite  discussion  of  the  probable  percentage  of  accuracy  of  his  results, 
as  such  a  discussion  would  have  added  greatly  to  the  value  of  the 
paper.  Mr.  Lee's  analyses  both  of  recharge  and  of  loss  are  excellent, 
but  in  order  to  reach  quantitative  conclusions  he  was  obliged  to  make 
numerous  assumptions  in  respect  to  both.  Although  these  assumptions 
were,  the  writer  believes,  made  carefully  and  with  good  judgment,  they 
must  have  introduced  considerable  errors  into  the  computations.  As 
assumptions  enter  into  both  estimates,  neither  one  can  be  regarded 
as  a  check  on  the  other.  The  fact  that  the  two  estimates  are  of  the 
same  magnitude  justifies  added  confidence  in  the  general  results,  but 
the  fact  that  they  differ  by  less  than  4%  does  not  indicate,  of  course. 


discussion:  yield  of  underground  reservoirs  237 

that  the  percentage  of  error  is  within  4%,  and  can  hardly  be  con-  j^^m.-.^^. 
sidered  a  confirmation  of  the  reliability  of  the  data  and  the  correctness 
of  the  assumptions  in  either  computation  (page  212). 

The  four  sources  of  percolation  are  given  as  (1)  direct  precipitation; 
(2)  stream  flow;  (3)  irrigation;  and  (4)  flood-water  in  the  valley  floor. 
It  is  assumed  that  the  high  mountain  areas  shed  all  precipitation  except 
that  which  is  lost  by  evaporation;  that  on  the  more  elevated  parts 
of  the  intermediate  mountain  slope  75%  of  the  precipitation, 
and  on  the  lower  parts  70,  65,  and  60%,  respectively,  join  the 
underground  supply;  that  the  contributions  to  the  underground 
supply  on  the  outwash  slopes  range,  according  to  zones,  from 
0  to  60%,  making  an  average  of  16%;  and  that  the  contribution 
on  the  valley  floor  is  4  sec-ft.  All  these  assumptions  are  based  on  care- 
ful, general  observations,  but  are  of  course  only  approximations  and 
subject  to  large  errors.  Moreover,  assumptions  are  involved  as  to  the 
areas  belonging  to  the  various  zones  and  the  amount  of  precipitation 
in  each  (page  206).  Several  assumptions  are  also  made  in  the  esti- 
mate of  recharge  from  stream  channels,  in  the  conclusion  that  50% 
of  the  irrigation  water  is  added  to  the  underground  supply,  and  in  the 
estimate  of  the  contributions  made  by  the  flood-waters. 

The  writer  agrees  with  Mr.  Lee  that  the  discharge  from  the  under- 
ground reservoir  can  be  determined  more  accurately  than  the  percola- 
tion into  it,  but  the  methods  of  estimating  discharge  also  involve  a 
number  of  elements  of  uncertainty.  If  the  writer  understands  rightly 
the  author's  discussion  of  the  discharge  from  irrigated  land,  the  50%, 
or  18  sec-ft.,  of  irrigation  water  discharged  by  evaporation  and  trans- 
piration (page  203)  is  the  portion  that  was  not  added  to  the  under- 
ground supply  (page  212)  and,  therefore,  should  not  be  included  with 
the  discharge  from  this  supply. 

The  largest  element  in  ground-water  discharge  is  that  of  evapora- 
tion and  transpiration  from  uncultivated  land.  It  is  on  this  question 
that  Mr.  Lee  has  made  his  most  important  contribution,  and  that  part 
of  his  paper  dealing  with  this  phase  of  the  subject  deserves,  therefore, 
the  most  critical  consideration.  Some  of  the  factors  that  enter  into 
this  estimate  were  determined  by  experiment  and  others  by  field 
survey.  Experimental  errors  were  involved  in  the  difference  between 
natural  and  artificially  packed  soils,  in  the  difference  between  the 
vegetation  in  Nature  and  in  soil  tanks  (pages  186,  187,  192,  and  193), 
in  uncertainties  as  to  the  actual  water-level  in  the  tanks  (pages  183 
and  184),  and  in  the  unavoidable  fluctuations  in  the  water-levels 
in  each  tank  (Tables  9  to  14,  inclusive).  These  experimental  errors 
are  represented  in  part  only  in  the  diagrams  in  Fig.  10.  In  the 
summer  diagram,  which  is  the  more  important  one,  the  results  from 
Tanks  ISTos.  5,  6,  and  7  fall  nearly  on  the  curve  used  by  Mr.  Lee  in 
his  calculations,  the  result  from   Tank  No.  4  being  more  than  20% 


238         discussion:  yield  of  underground  reservoirs 

Mr.  too  low,  that  of  Tank  No.  3  more  than  20%  too  high,  and  that  of 
Meinzer.  rp^^j^  jq-^  2  nearly  40%  too  low.  It  should  be  noted,  however,  that 
although  these  results  involve  large  experimental  errors,  they  corrobo- 
rate each  other  in  a  general  way  and  are  of  great  value  in  furnishing 
reliable  data  on  the  general  magnitude  of  one  of  the  most  important 
processes  in  ground-water  circulation. 

In  applying  the  experimental  data  to  the  basin  under  investigation, 
inaccuracies  were  involved  in  the  sizes  of  the  areas  having  specified 
depths  to  the  water-table,  in  the  fluctuations  of  the  water-table,  in 
difference  in  the  range  and  rate  of  capillary  rise  due  to  difference  in 
the  character  of  the  soil,  and  in  difference  in  the  density  of  vegetation 
and  kinds  of  plants  that  draw  water  from  the  underground  reservoir. 
An  error  was  also  involved  in  the  fact  that  observations  covering  only 
1,  2,  or  3  years  did  not  give  average  evaporation  conditions,  just  as 
precipitation  and  stream-gauging  data  for  a  period  of  the  same  length 
do  not  afford  reliable  averages.  With  142  observation  wells  on  the 
valley  floor  (page  197),  the  error  as  to  the  water-table  cannot  have 
been  large,  yet  the  rate  of  discharge  varie.«  so  greatly  with  small  changes 
in  depth  of  the  water-table  that  even  slight  inaccuracies  in  determining 
one  produce  appreciable  errors  in  calculating  the  other.  Although  the 
valley  floor  in  that  part  of  Owens  Valley  investigated  by  Mr.  Lee  has 
relatively  uniform  conditions,  there  is  luxuriant  salt  grass  in  some  parts 
and  an  entire  absence  of  vegetation  in  others  (page  161),  whereas  the 
experiments  did  not  cover  these  different  conditions.  Moreover,  no 
account  was  taken  of  the  zone  having  depths  to  the  water-table  between 
8  and  12  ft,  although  the  greasewood  and  rabbit  brush  in  this  zone 
probably  draw  water  from  the  underground  reservoir  (page  198). 

The  writer  agrees  with  Mr.  Lee  that  the  evaporation  method  is 
the  most  feasible  one  for  estimating  ground-water  recharge  in  many 
of  the  debris-filled  basins,  especially  where  there  are  as  yet  few  devel- 
opments, but  its  application  is  far  from  being  a  simple  matter.  The 
data  which  he  obtained  in  Owens  Valley  have  value  in  making  rough 
estimates  of  annual  recharge  in  valleys  in  which  the  evaporation  areas 
are  mapped  and  reliable  observations  are  made  as  to  the  character 
of  the  soil  and  vegetation  and  the  distance  to  the  water-table  in  the 
different  zones  of  such  areas,  but  to  assure  any  considerable  degree 
of  accuracy  for  most  valleys  it  will  be  necessary  not  only  to  sink  a 
large  number  of  observation  wells  and  to  keep  them  under  observation 
for  one  or  more  years,  as  was  done  in  Owens  Valley,  but  also  to 
obtain  a  great  deal  more  information  as  to  the  rate  of  discharge  under 
various  conditions  of  soil  and  vegetation.  The  conditions  in  the 
evaporation  areas  of  most  valleys  are  far  from  uniform,  the  soil  ranging 
from  dense  clay  to  coarse  sand  or  gravel,  and  the  vegetation  embracing 
.a  number  of  diverse  species  and  being  entirely  absent  over  large  tracts. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS  239 

The  writer  wishes  to  urge  the  importance  of  further  investigations  Mr. 
along  the  lines  suggested.  The  lowest  parts  of  many  of  the  closed 
basins  are  underlaid  by  clay  cores  destitute  of  vegetation  but  sur- 
rounded by  zones  of  less  dense  soil  in  which  evaporation  and  transpira- 
tion are  active.  The  dissemination  of  the  soluble  salts  instead  of  their 
concentration  at  the  surface  and  other  conditions  lead  him  to  believe 
that  on  these  clay  cores  the  ground-water  discharge  is  sluggish,  but 
definite  tests  are  needed  as  to  the  quantity  of  discharge  and  its  rela- 
tion to  the  distribution  of  the  soluble  salts.  Among  the  common  native 
plants  (besides  the  salt  grasses)  which  apparently  discharge  ground- 
water, are  samphire  (Spirostachys  occidentalis) ,  iodine  weed  (Suaeda), 
alkaline  sacatcn  (Sporoholus  airoides),  certain  species  of  salt  bush 
(Atriplex),  big  greasewood  (Sarcohatus  vermiculatus),  rabbit  brush 
(Chrysothamnus  graveolens),  buffalo  berry  bush  (Shepherdia) ,  and 
mesquite  (Prosopis).  Mesquite  does  not  thrive  in  the  shallow-water 
areas  where  the  soil  is  dense  and  alkaline,  but  is  often  dominant  in  a 
zone  of  moderate  depth  to  water  surrounding  a  shallow-water  area. 
It  is  important  to  know  whether  the  mesquite  actually  feeds  on  ground- 
water, and  if  so,  from  what  depth  and  at  what  rate  it  is  able  to  lift 
this  water  to  the  surface. 

Mr.  Lee's  final  conclusions  (page  218)  sum  up  admirably  the 
esssential  factors  in  the  problem  of  safe  yield.  As  it  is  not  generally 
practicable  to  draw  any  large  part  of  the  ground-water  of  one  segment 
of  a  valley  to  another,  a  proper  distribution  of  wells  is  necessary  in 
order  to  reduce  the  residual  losses  to  the  lowest  possible  quantity. 
Overdraft  with  serious  lowering  of  the  water-table  may  occur  in 
certain  segments  while  evaporation  of  ground-water  contributed  by 
other  segments  is  still  in  progress  on  the  lowest  lands.  Such  loss  can 
be  prevented  only  by  increased  withdrawals  in  the  undeveloped  seg- 
ments, and  if  these  segments  have  little  or  no  land  that  can  be  profitably 
irrigated,  the  loss  may  be  unavoidable. 

Kenneth  Allen,*  M,  Am.  Soc.  C.  E.  (by  letter). — Underground  Mr. 
water  supplies,  as  well  as  surface  supplies,  depend  on  the  rainfall,  the  ^"^"' 
catchment  area,  and  the  available  storage,  with  its  accompanying  losses 
by  overflow,  leakage,  and  evaporation;  but  the  problem  for  the  engi- 
neer is  more  difficult  in  the  case  of  underground  supplies,  as  the  true 
limits  of  the  catchment  area,  the  storage  capacity,  and  the  probable 
amount  of  the  losses  mentioned  can  only  be  determined  approximately 
after  a  pretty  thorough  examination  of  the  sub-surface  conditions,  that 
is,  the  configuration  of  the  permeable  strata,  their  impermeable  confines, 
and  their  physical  characteristics — permeability,  etc.  In  the  majority 
of  cases  much  of  this  information  is  inaccessible,  and  more  or  less 
dependence  is  placed  on  such  collateral  evidence  as  the  yield  of  neigh- 
boring wells  and  the  results  obtained  by  sinking  test  wells. 

*  New  York  City. 


240         DISCUSSION :  yield  of  underground  reservoirs 

Mr.  The  limitations  imposed  by   enclosing  impervious  formations  and 

■^''*^°"  by    sub-surface    evaporation    are    clearly    and    interestingly    presented 
by  tlie  author,   and   their  importance   is  shown  under  the  conditions 
discussed.      In   most   well   developments,    however,   evaporation    is   of 
minor  significance.     This  is  not  only  on  account  of  greater  humidity, 
but  because   most  supplies  percolate  through   an   unenclosed   stratum 
for  perhaps  many  miles  and  because  evaporation  from  this  stratum  is 
usually  prevented  by  the  superposition  of  one  or  more  impervious  strata. 
In  practice  the   available  yield   is   subject   to   further   limitations. 
The  water-bearing  stratum  may  consist  of  an  impervious  rock   con- 
taining crevices  or  tissures  due  to  movements  in  the  earth's  crust,  or 
water-courses  caused  by  the  solvent  action  of  the  water  itself.     The 
latter  are  of  frequent  occurrence  in  limestone  and  chalk  formations 
and  the  former  in  sandstones  and  the  denser  igneous  rocks.     Fissures 
occur  more  frequently  near  the  surface  than  at  great  depths,  and,  as 
the  cost  of  drilling  increases  with  the  depth,  deep  borings  in  search 
of  water-bearing  fissures   are  not  often  profitable.     The  same  money 
can  be   spent   to  better  advantage  in  making  several  test  borings  at 
moderate  depth.     Although  the  results  of  such  borings  are  uncertain, 
supplies,   when   obtained   from   fissures,    are   often    abundant    and   the 
wells   free   from   the  clogging   so   often   experienced  with   sand.      The 
yield  of  a  well  in  sand  is  directly  limited  by  the  porosity  of  the  latter 
and  the  available  head.     In  fine  sands  there  is  a  large  loss  of  head  due 
to  percolation  near  the  strainer   in  order  to  maintain  the  necessary 
flow.     This   difficulty  may  be   overcome  by   increasing  the  length   of 
the  strainer,  if  this  does  not  exceed  the  thickness  of  the  water-bearing 
stratum,  but  this  is  at  the  expense  of  a  greater  first  cost  as  well  as 
an  increase  in  lift  due  to  the  fineness  of  the  material.     In  such  cases 
the  loss   of   head   is   often   reduced  by   removing  the   sand   about  the 
strainer  and  filling  the  pocket  with  gravel,  or  else  by  substituting  a 
larger  number  of  driven  well  points  from  2  to  3  in.  in  diameter  for 
the  large  (6  to  12-in.)  casing  and  strainer. 

In  those  cases  where  the  water  occurs  in  a  stratum  of  fine  sand 
of  small  thickness,  the  difficulty  is  further  increased.  The  writer  tested 
a  stratum  of  this  kind  several  years  ago  with  the  view  of  developing 
a  supply  of  some  5  000  000  gal.  daily  for  a  southern  city.  Water 
was  found  in  apparent  abundance  throughout  a  large  area  at  a  mod- 
erate depth,  the  land  was  low,  covered  with  forest,  not  far  from  a 
stream  of  considerable  size,  and  on  it  were  several  large  springs.  On 
sinking  numerous  test  wells  on  a  line  about  4  miles  long,  however, 
it  was  shown  that  the  water-bearing  stratum,  besides  being  of  a  fine 
sand,  was  so  thin  that  the  cost  of  developing  the  desired  supply  would 
be  prohibitive. 

Water  supplies  found  in  deep  deposits  of  sand  or  drift,  especially 
those   derived   from   distant   and   extensive   catchment   areas,   such    as 


discussion:  yield  of  underground  reservoirs 


241 


exist  south  of  the  great  terminal  moraine  on  the  south  side  of  Long  Mr. 
Island  and  on  the  Atlantic  Coastal  Phiin  from  Sandy  Hook  to  Florida, 
are  most  favorable  for  development.  Well-known  examples  are  the 
1  400-ft.  Ponce  de  Leon  well  at  St.  Augustine,  said  to  furnish  10  000  000 
gal.  daily,  and  the  1  970-ft.  well  at  Charleston,  furnishing  1  250  000 
gal.  daily.  On  the  other  hand,  a  well  was  bored  in  1900-01  at  Atlantic 
City,  N.  J.,  to  a  depth  of  2  306  ft.  (below  the  floor  of  Young's  Pier), 
and  although  a  good  supply  was  found  between  depths  of  780  and  860 
ft.,  in  a  stratum  of  sand  tapped  by  numerous  wells  in  the  vicinity, 
the  supply  sought  at  the  greater  depth  was  not  realized,  and  the  well, 
then  the  deepest  but  one  along  the  Atlantic  Coast,  was  abandoned. 


Pump  Wells 

oOO    ^ 


I  Pumping 
I  Station 


Note:    Wells  Nos.3  and  12  were  old  ones. 

Well  No.2,  200  ft.  deep.    All  others,  100  ft. 

Well  No.2,  6-in.,  Well  No.l2,  4K-ir».    AH  others  10-in. 

Wells  operated  in  test,  Nos.l,  3,  4.  5,  6,  7,  8,  9,  10,  11,  and  12. 

Scale  of  Feet 
0  200  400  600 


Fig.  15. 

About  5  miles  inland,  the  Water  Department  had  a  small  collecting 
basin  near  its  pumping  station  (Fig.  15),  in  which  were  driven  a 
number  of  4-in.  tubes  tapping  a  water-bearing  stratum  24  ft.  below. 
Near  the  basin  was  a  10-in.  well  (No.  3)  extending  to  a  depth  of  about 
100  ft.  to  another  water-bearing  stratum  which  it  was  proposed  to 
develop  as  an  additional  supply  to  the  extent  of  3  000  000  or  4  000  000 
gal.  daily.  The  capacity  of  this  well  was  first  tested  by  erecting  over 
it  an  old  1 000  000-gal.  Worthington  pump,  which  the  Department 
had,  and  connecting  it  with  a  steam  line  to  the  boiler  plant  at  the 
station.  During  a  6-hour  test  with  a  19-in.  vacuum  on  the  suction, 
the  delivery  was  practically  uniform  at  a  rate  of  840  000  gal.  per  day, 
and  as  no  downward  flow  was  observed  in  the  small  tubes  in  the  basin, 
it  was  concluded  that  there  was  no  connection  between  these  two  strata. 
On  the  strength  of  this  test,  ten  10-in.  wells,  125  ft.  apart,  were  sunk 
to  a  depth  of  about  100  ft.  and  a  6-in.  well  (No.  2)  to  a  still  deeper 


242  DISCUSSION :  yiel-d  of  underground  reservoirs 

Mr.  stratum,  200  ft.  below  the  surface.  Besides  these  there  were  two  old 
®°'  wells — the  10-in.  well  tested  with  the  steam  pump  and  a  4i-in.  well 
(No.  12),  both  of  which  were  carried  to  the  100-ft.  stratum.  The 
deeper  6-in.  well  flowed  freely  at  a  rate  of  66  000  gal.  per  day 
and,  by  use  of  the  air  lift,  at  a  rate  of  400  000  gal.  per  day, 
or  about  280  gal.  per  min.  The  10-in.  wells  on  short  separate  tests 
produced  from  150  to  400  gal.  per  min.  Ten  of  the  10-in.  wells  (No.  1 
and  Nos.  3-11)  and  the  4^-in.  well  (No.  12)  were  then  connected  with 
the  compressor  and  given  a  6-hour  test.  These  wells  together  delivered 
846  879  gal.,  or  at  a  rate  of  3  705  492  gal.  per  day.  This  was  an  aver- 
age of  336  866  gal.  per  well,  or  60%  less  than  the  delivery  from  Well 
No.  3  when  operated  alone.  Moreover,  the  average  lift  in  this  well 
during  the  test  was  24.56  ft.,  though  the  vacuum  gauge  on  the  suction 
during  the  earlier  separate  test  indicated  a  lift  of  21  ft.  to  about 
the  same  level.  Assuming  this  well  to  have  produced  one-eleventh 
of  the  total  quantity  during  the  combined  test,  the  effect  of  interference 
from  the  other  wells,  while  operating  all  eleven  at  this  rate,  was  to 
increase  the  lift  by  about  3.6  ft.  while  reducing  the  output  by  60 
per  cent. 

The  yield  under  conditions  found  along  the  Coastal  Plain  region 
bears  little  relation  to  that  from  underground  reservoirs  of  the  closed- 
basin  type  described  by  the  author,  but  somewhat  similar  conditions 
are  met  in  the  basin  of  the  prehistoric  Lake  Passaic  of  Northern  New 
Jersey.  Wells  in  the  outlet  of  this  lake,  now  filled  with  glacial  drift, 
furnish  the  water  supply  for  East  Orange.  When  first  sunk,  several 
of  these  6-in.  and  8-in.  wells  had  a  natural  flow  of  from  400  to  500 
gal.  per  min. 

Above  this  outlet  water-bearing  sandstones  underlie  the  ancient 
lake,  but  percolation  to  these  beds  is  cut  off  on  the  northwest  by  the 
trap  dikes  forming  the  Orange  or  Wachung  Mountains  and  on  the 
southeast  by  the  Palisades  of  the  Hudson.  Assuming  a  general 
southerly  flow,  percolation  from  a  distance,  therefore,  is  limited  to  that 
from  the  northeast,  the  limit  in  this  direction,  it  is  believed,  being 
unknown. 

These  sandstones,  nevertheless,  furnish  a  large  number  of  excel- 
lent well  supplies  in  the  vicinity  of  Newark  and  Paterson,  chiefly  by 
means  of  their  numerous  fissures.* 

Data   concerning  a  large  number  of  these  wells,  collected  by  the 

writer  a  few  years  ago,  indicate  a  great  variation  in  the  yield.     They 

are  commonly  from  100  to  500  ft.  in  depth,  and  6  or  8  in.  in  diameter, 

and  generally  furnish   from  20  to   200  gal.   per  min.   each,   although 

failures  are  not  infrequent,  and  several  produce  as  much  as  500  gal. 

per  min. 

♦Report,  state  Geologist  of  New  .lersey.  1903,  p.  79;  also  Water  Supply  and  Irrigation 
Papers.  U.  S.  Geological  Survey,  No.  114,  p.  96. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS 


243 


ATMOMETER  WITH  AUTOMATIC 
SUPPLY  AND  CONSTANT       B^ 
WATER   LEVEL 


KoBERT  E.   HoRTON*  M.   Am.   Soc.  C.  E.   (by  letter). — This  paper     Mr. 
bears  abundant  evidence  of  being  the  work  of  an  accomplished  hydrolo- 
gist,  and  specially  commends  itself  to  the  writer  because  it  represents 
the  combined  application  of  studies  of  the  rainfall  and  run-off  relations 
of  the  basin  itself  with  laboratory  experiments  on  evaporation  losses. 

For  many  purposes  in  hydrologic  work,  laboratory  experiments 
are  capable  of  yielding  very  instructive  results  because  the  problems 
in  N'atvire  are  often  so  complex  as  to  make  it  difficult  to  separate 
effects  produced  by  one  cause  from  those  produced  by  a  combination 
of  causes.  After  studying  the  completed  results,  various  ways  sug- 
gest themselves  by  which  the  experimental  data  might  have  been 
improved.  The  writer,  however,  refrains  from  criticism  in  this  regard, 
fully  realizing  how  difficult  it  is  at  the  outset  to  determine  the  best 
lines  or  methods  of  investigation  and  how  to  prepare  in  advance  for 
conditions  which  may  arise  unexpectedly  in  the  progress  of  the  work. 

The  paramount  problem  in  applied  hydrology  is  the  utilization 
of  existing  data  for  a  locality, 
whatever  the  data  may  be,  and 
whether  complete  or  incomplete, 
so  as  to  derive  therefrom  the 
best  possible  solution  of  the 
specific   problem. 

The    writer    feels    that    Mr. 
Lee's  work  in  the  acquisition  of 
data  has  been  somewhat  in  ad- 
vance   of    his    analysis    of    the 
results,    in    that    the    work    of 
other  experimenters  on  the  ques- 
tion of  soil  evaporation,  and  transpiration  in  particular,  might  have 
been  analyzed  and  to  some  extent  utilized  to  advantage  in  this  case. 
For  example,  it  would  seem  that  the  difficulties  experienced  in  obtaining 
constant  ground-water  table  in  the  soil  evaporameters  should  have  been 
foreseen.     Quite  similar  experiments  were  carried  out  successfully  by 
Ebermayer  many  years  ago,  using  the  apparatus  shown  in  Fig.  16,  in 
which  the  lower  surface  of  the  soil  prism  is  maintained  constantly  in 
contact  with  the  water  surface  by  an  automatic  air  valve  in  the  reser- 
voir,  C.     The  uplifting  of  water  from  the  soil  prism  is  entirely  the 
result  of  capillary  action.f 

The  writer  has  not  had  opportunity  to  examine  Water  Supply 
Paper  No.  294,  which  presumably  contains  detailed  results  of  the 
observations  of  precipitation  and  run-off.  It  would  have  added  to 
the  value  and  interest  of  the  paper  if  Mr.   Lee  had  included  tables 


Fig.  16. 


*  Albany,  N.  Y. 

t  A  full  description  of  Ebermayer's  experiments  and  results  is  given  in  a  paper  by  the 
writer  in  The  Michigan  Engineer,  1918-14,  pp.  66-89. 


244  DISCUSSION :  yield  of  underground  reservoirs 

Mr.  showing  the  monthly  precipitation  and  run-off  of  the  different  streams, 
■  because  it  is  unusual  to  find  records  o£  the  attendant  conditions 
available  in  conjunction  with  stream  flow  data,  as  is  the  case  here. 
Mr.  Lee  states  that  the  flow  of  the  mountain  gulch  streams  tribu- 
tary to  Owens  Valley  is  practically  constant  throughout  the  frozen 
season.  This  statement  is  only  relatively  true.  From  the  data 
relating  to  these  streams  appearing  in  Water  Supply  Paper  No.  300, 
their  yield  varies  100%  or  even  more,  there  being  generally  a  gradual 
decrease  in  flow  from  the  beginning  to  the  end  of  the  frozen  season. 
Attention  is  called  to  this  point  principally  because  a  fundamental 
principle  of  the  regimen  of  streams  is  commonly  overlooked,  namely, 
that  a  stream  or  spring  cannot  yield  a  constant  outflow  throughout 
any  considerable  period  of  time  unless  there  are  simultaneous  addi- 
tions to  the  available  water  supply.  In  the  case  of  the  mountain 
streams  in  question,  the  winter  precipitation  occurs  as  snow  and 
remains  frozen  generally  throughout  that  period,  thus  eliminating  any 
increment  of  supply  to  the  streams  from  surface  water.  Presum- 
ably there  is  a.  ground-water  reservoir  from  which  these  streams  are 
gradually  fed  throughout  the  winter.  This  ground-water  reservoir 
must  of  necessity  be  gradually  depleted  and  the  flow  of  the  streams 
gradually  decreased,  as  appears  to  be  the  case.  This,  however,  brings 
up  an  interesting  problem.  It  appears  possible,  and  indeed  probable, 
that  in  many  instances  waters  which  have  previously  entered  the  soil 
but  remain  above  the  zone  of  saturation — or,  in  other  words,  above 
the  ground-water  table  tributary  to  the  stream — gradually  percolate 
downward,  entering  the  body  of  ground-water  and  aiding  to  maintain 
a  constant  supply  through  long  periods  of  drought  or  during  the 
winter  when  surface  supply  and  infiltration  are  shut  off.  If  the 
rate  of  addition  to  the  ground-water  body  is  greater  than  the  initial 
rate  of  outflow  therefrom,  the  ground-water  table  will  gradually  rise 
to  such  a  height  that  the  outflow  will  become  equal  to  the  inflow  from 
percolation,  and  then,  as  long  as  the  downward  percolation  remains 
substantially  constant,  the  yield  of  the  stream  also  will  remain 
constant. 

JVIr.  Lee's  paper  brings  out  forcibly  an  important  hydrologic  fact 
often  overlooked,  namely,  that  very  substantial  yields  of  water  may 
often  be  obtained  permanently  from  undrained  depressions  or  closed 
basins  where  naturally  the  entire  precipitation  is  lost  through  evapo- 
ration. To  accomplish  this  it  is  only  necessary  to  reduce  the  evapora- 
tion as  much  as  possible  below  the  inflow  from  precipitation.  This, 
as  pointed  out  in  the  paper,  will  naturally  result  if  the  ground-water 
table  is  drawn  down  permanently  below  the  limit  of  capillary  uplift 
and  evaporation  from  the  soil,  and  below  the  limit  of  absorption  by 
plant  roots. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS  245 

Mr.  Lee  describes  the  typical  geological  construction  of  a  moun-  Mr. 
tain  fault  basin  as  the  result  of  the  product  of  faulting  accompanied 
by  the  uptilting  of  a  crustal  block  from  one  side  of  the  line  of  fracture. 
Fault  valleys  of  this  type  are  not  uncommon  in  the  East.  One  of 
these,  in  the  eastern  slope  of  the  Helderbergs,  not  far  from  Albany, 
is  known  to  the  writer.  In  this  case  a  section  of  the  valley  is  appa- 
rently somewhat  as  shown  in  Fig.  17.  It  appears  to  the  writer  prob- 
able that  in  this  case,  and  no  doubt  frequently  in  other  cases,  there 
are  more  or  less  debris-filled  spaces,  A  and  B,  between  the  ends  of 
the  tilted  blocks  and  the  fault  face.  As  a  result,  there  are  likely  to 
be  subterranean  outlets  from  the  valley  through  the  spaces,  A  and  B, 
at  greater  or  less  depths  below  the  junction  of  the  valley  surface  rock 
with  the  fault  face  at  C.  In  the  vicinity  referred  to,  frequent  illus- 
trations of  tilting  and  overthrust  of  underlying  strata  can  be  seen. 
Evidence  of  subterranean  channels  along  the  fault  line  beneath  the 
rock  floor  of  the  valley  appears  from  ^^^^^  ^^  fountain  valley  formation 
the  fact  that  the  only  visible  outlet 
of    drainage    from    the    valley    is  \ 

through  a  very  large  and  perma- 
nent spring  which  comes  to  the 
surface  along  a  continuation  of  the 
fault  line  at  a  distance  of  about  a 
mile  from  the  lower  end  of  the  val- 
ley and  at  the  point  where  the 
fault  line  crosses  the  valley  of  a 
large  stream. 

This  instance,  and  the  frequent 
occurrence  of  undrained  depres- 
sions in  the  East,  suggests  to  the 
writer  the  fact  that  the  underlying 

principles  of  hydrology  are  very  general,  and  the  conditions  widely 
distributed  throughout  the  earth.  Unfortunately,  the  range  of  con- 
ditions is  not  as  well  recognized  as  it  should  be,  and  it  is  probably 
due  to  this  fact,  rather  than  to  differences  in  the  classes  of  conditions 
to  be  met,  as  classes,  that  there  have  been  so  many  wild  and  erroneous 
estimates  of  the  available  yield  of  water  supplies.  In  view  of  the 
limited  experiments  and  studies  which  have  been  made  along  scientific 
lines  such  as  those  carried  out,  for  example,  by  Mr.  Lee,  for  the  solu- 
tion of  specific  problems,  it  becomes  an  increasing  matter  of  wonder- 
ment to  the  writer  that  serious  mistakes  and  miscalculations  in  the 
available  water  supply  for  municipalities  or  for  power  or  other  pur- 
poses have  not  more  often  been  made. 

It  is  often  the  case  that  the  success  or  failure  of  a  hydraulic 
project  depends  primarily  on  the  water  supply,  yet,  as  a  rule,  much 
less  attention  is  given  to  the  scientific  determination  of  this  element 


Fig.   17. 


24:6  DISCUSSION :  yield  of  undeeground  reservoirs 

Mr.     than  to  many  much  less  important  structural  elements.     The  writer 
Horton.  |g  pleased  to  see  in  the  present  instance  the  hydrologic  side  of  the 
question  at  issue  given  apparently  its  due  share  of  attention. 

The  writer  feels  obliged  to  take  exception  to  Mr.  Lee's  statement 
that  the  transpiration  from  plants  is  independent  of  the  humidity. 
The  elegant  experiments  along  this  line  by  Ganung,  in  connection 
with  which  graphic  records  of  transpiration  and  of  the  accompanying 
meteorological  elements,  light,  humidity,  and  temperature,  were 
obtained,  illustrate  quite  conclusively,  it  would  seem,  that  there  is  a 
fairly  definite  relation  between  transpiration  rate  and  humidity.* 

Mr.  Lee  has  proved  that  the  increase  in  rainfall  on  mountain  slopes 
is  more  nearly  proportional  to  the  slope  gradient  than  to  the  absolute 
humidity.  It  seems  necessary  to  call  attention  to  the  distinction 
between  the  increase  in  atmospheric  precipitation  which,  as  shown 
by  the  classic  researches  of  Pockels,  is  directly  the  result  of  dynamic 
cooling  and  consequently  is  a  function  of  the  elevation  of  a  mass  of 
air,   nearly  or  quite  independent 

J.   -^     T         •  ^    T   ^  +4.-  •  RELATION  OF  RAINFALL  INCREASE 

of. its  horizontal  transportation  m           ^^  gradient  on  mountain  slopes 
the  meantime,   on  the  one  hand,                          m'  n' 

and  the  increase  in  precipitation  L-| 1^     ^. 

on    the    ground    surface,    on    the  _^''^     j^  r  /  A    / 

other    hand.      The    difference    is    i^-'"    jy.  _  J___^/__r^Lj  / 
illustrated  by  Fig.  18.     Consider    Ln'"  ^^  t_]    / 

two  masses  of   air  of  equal  vol-      |  i 

ume,  M  and  iV,  respectively,  ap-      '  ^ 

proaching  the  slopes  AB  and  CD. 
Let  both  masses  be  initially  at  the  same  height,  and  let  both  be  elevated 
throughout  the  same  height,  h,  to  the  positions,  W  and  W.  The  same 
quantity  of  precipitation  will  be  produced  from  each  mass  of  air.  Pf 
the  gradient,  CD,  is  twice  as  steep  as  the  gradient,  AB,  the  resulting 
precipitation  on  the  flat  slope,  AB,  will  be  distributed  over  twice  as 
great  an  area  as  that  on  the  slope,  CD,  as  is  evident  from  the  diagram. 
Thus  the  apparent  increase  in  precipitation  will  be  proportional  to 
the  slope  gradient. 

The  peculiar  condition  existing  in  the  case  of  triangular  mountain 
drainage  areas,  whereby  the  mean  precipitation  occurs  at  the  center  of 
area  of  the  drainage  basin,  illustrates  the  importance  of  weighting  rain- 
fall records,  taken  at  different  portions  of  a  drainage  basin,  in  propor- 
tion to  the  relative  part  of  the  total  area  which  each  one  represents. 
This  practice  has  been  followed  by  the  writer  for  a  number  of  years 
in  estimating  mean  rainfall  on  drainage  areas.  The  necessity  for 
the  use  of  such  a  process  arises  partly  from  the  fact  that  rainfall 
stations  are  most  commonly  located  in  stream  valleys.  In  the  case 
of  triangular  basins,  similar  to  those  tributary  to  Owens  Valley,  but 

*  "  The  Living  Plant,"  by  W.  F.  Ganung,  p.  204. 


Fig.   18. 


DISCUSSION  :    YIELD   OF   UNDERGROUND   RESERVOIRS  247 

for  the  extreme  condition  of  zero  precipitation  at  the  mouth  of  the     Mr. 
stream,  the  average  of  a   line  of  equidistant  rainfall  stations  located 
along  the  stream  from  its  source  to  its  mouth,  would  give  an  apparent 
mean  precipitation  for  the  area  only  five-sixths  as  great  as  the  true 
mean  precipitation,  or  the  error  would  be  163%  of  the  true  mean. 

Charles  II.  Lee,*  Assoc.  M.  Am.  Soc.  C.  E.  (by  letter). — Realizing  Mr. 
the  somewhat  local  character  of  his  paper,  the  writer  has  been  highly 
gratified  to  find  that  it  has  brought  forth  discussion  based  on  such 
widely  divergent  as  well  as  similar  experience.  He  especially  appre- 
ciates the  broad  and  constructive  contributions  of  Messrs.  Smith  and 
Meinzer,  whose  wide  experience  with  ground-water  problems  qualifies 
them  to  speak  with  authority. 

The  writer  heartily  agrees  with  Mr.  Owen  that  there  is  a  great 
need  in  all  sections  of  the  United  States  for  definite  scientific  knowl- 
edge regarding  the  principles  which  should  govern  ground-water  de- 
velopment. He  would  not,  however,  place  such  knowledge  in  the 
realm  of  the  unattainable,  as  both  Messrs.  Owen  and  Allen  in  their 
opening  paragraphs  seem  inclined  to  do.  The  Engineering  Profession 
has  already  made  considerable  progress  in  the  formulation  and  appli- 
cation of  such  principles.  In  Europe,  for  instance,  where  the  demand 
for  municipal  water  supplies  has  reached  the  point  where  the  limit 
of  every  available  source  must  be  known,  there  has  been  accumulated 
such  a  fund  of  knowledge  derived  from  investigation  and  experience 
that  the  subject  is  recognized  as  a  distinct  branch  of  the  Profession. 
In  the  United  States  the  exhaustive  investigations  of  ground-water 
supply,  such  as  that  made  on  Long  Island  by  the  City  of  New 
York  and  the  work  of  the  United  States  Geological  Survey,  show  that 
in  America,  also,  the  subject  has  advanced  far  beyond  the  stage  of 
conjecture.  It  is  the  writer's  opinion  that  the  time  is  now  ripe  for 
the  formulation  of  general  principles  and  methods  of  investigation 
and  development  of  ground-water  among  American  engineers,  and  it 
was  with  this  in  view  that  his  paper  was  written.  It  is  to  be  hoped 
that  similar  papers  will  be  presented  by  members  of  the  Society  who 
have  had  opportunity  to  study  other  types  of  ground-water  occurrence, 
in  order  that  a  more  complete  presentation  of  the  subject  in  its  most 
recent  development  may  become  available  to  the  Profession. 

The  writer  was  much  interested  in  the  statements  of  both  Messrs. 
Smith  and  Meinzer  that  the  term  "water-tight"  as  applied  to  ground- 
water reservoirs  is  a  relative  one,  and  that,  in  many  arid  States,  it 
does  not  apply  at  all.  Their  experience  and  the  writer's  more  recent 
observations  outside  of  California  are  in  accord  in  this  matter,  and 
the  first  conclusion  of  the  paper  (page  149)  should  be  modified  accord- 
ingly.   In  all  the  California  basins  which  have  come  under  the  writer's 

*  Los  Angeles,  CaL 


248  discussion:  yield  of  underground  reservoirs 

Mr.   observation,  however,  the  term  can  be  used  for  all  practical  purposes. 

^^^'  These  basins  occur  either   in   granite   or   in   tertiary   sandstones   and 
.shales,    and,   as   the  fill   is   recent,   the   difficulty   encountered   by   Mr. 
Smith  in  defining  the  basin  seldom  arises. 

Both  Messrs.  Meinzer  and  Smith  have  commented  on  transpira- 
tion losses,  and  the  latter  has  contributed  the  first  really  useful  state- 
ment of  basic  principles  which  the  writer  has  seen.  It  is  to  be  hoped 
that  further  work  will  be  done  to  confirm  the  principle  of  equal  rela- 
tive rates  of  transpiration,  and  that  quantitative  determination  be 
made  of  the  ratio  between  evaporation  and  transpiration.  In  all  such 
experiments  care  should  be  taken  to  measure  evaporation  under  some 
standard  condition,  for,  as  is  well  known,  the  results  derived  from 
pans  in  large  bodies  of  water,  in  wet  soil,  in  dry  soil,  and  in  air,  differ 
widely,  and  in  the  same  environment  differ  with  atmospheric  exposure. 
In  this  connection  the  writer  wishes  to  call  attention  to  the  fact 
that  Mr.  Smith's  conclusion  (page  226)  that  the  combined  loss  by 
evaporation  and  transpiration  from  salt-grass  sod  is  twice  that  from 
damp  soil  alone  is  not  justified.  The  rate  of  water  evaporation  from 
the  deep  tank  in  the  soil  far  exceeded  that  from  soil  during  the  winter, 
for  the  reason  that  the  soil  was  kept  cold  by  evaporation  and  cold 
air  temperature,  while  the  water  was  free  to  circulate  and  received 
warmth  from  the  deeper  soil.  Experiments  (which  the  writer  carried 
on  but  did  not  publish)  indicate  that  the  annual  evaporation  from 
saturated  base  soil  is  about  93%  of  that  from  the  water  surface  in 
the  deep  tank.  The  combined  transpiration  and  soil  evaporation  for 
similar  conditions  was  115  per  cent. 

With  these  general  observations  the  writer  will  pass  on  to  detailed 
comments  on  the  discussion  of  the  paper.  Mr.  Smith's  paragraphs, 
grouped  under  the  head  of  "Estimates  of  Safe  Yield"  (pages  231-234), 
will  be  taken  up  first. 

1.  The  conditions  on  the  slopes  of  the  Catalina  -and  Eincon  Moun- 
tains, described  by  Mr.  Smith,  are  not  as  similar  to  those  of  the  east 
slope  of  the  Sierra  Nevada  as  would  appear  at  first  glance.  Table  3 
shows  that  the  lowest  elevation  of  the  Sierra  slopes  is  6  500  ft.,  the 
average  7  500  to  8  000  ft.,  and  the  maximum  elevation  12  000  ft. 
The  similar  slopes  back  of  Tucson  extend  from  an  elevation  of  3  000 
to  about  6  000  ft.  The  Sierra  slopes  do  not  support  a  luxuriant  desert 
vegetation  nor  forest  growth,  the  latter,  especially,  being  spotted  and 
sparse.  The  precipitation  on  the  Sierra  slopes  is  all  in  the  form  of 
snow,  which  melts  and  sinks  into  the  porous  mantle  before  the  growing 
season  commences.  On  the  intermediate  slopes  of  the  Catalina  Moun- 
tains, however,  the  precipitation  occurs  largely  in  severe  summer 
storms,  from  which  the  run-off  is  rapid  and  the  percolation  is  imme- 
diately available  to  vegetation.  These  differences  are  all  such  as  to 
favor  greater  percolation  on  the  Sierra  slope.     Furthermore,  there  are 


discussion:  yield  of  underground  reservoirs  249 

numerous  springs  at  the  base  of  the  Sierra  slopes,  the  flow  of  which,  in  ^r 
many  cases,  can  be  measured  in  second-feet  instead  of  cattle  drinks. 
Hence,  the  writer  still  believes  that  the  run-off  coefficients  used   are 
not  excessively  high. 

2.  Charlies  Butte  is  a  low  mound  of  lava  near  the  margin  of  a 
shallow  flow  which  advanced  out  over  the  valley-fill.  The  Butte  is 
not  the  crest  of  a  bed-rock  projection,  as  Mr.  Smith  suggests,  but  is 
superimposed  on  the  valley-fill.  The  spring  is  of  the  type  described 
by  the  writer  on  page  175,  and  unquestionably  has  its  source  in  per- 
colation from  the  outwash  slope. 

3.  The  writer  believes  that  Mr.  Smith  is  justified  in  giving  a 
value  to  transpiration  from  the  luxuriant  desert  vegetation,  the  roots 
of  which  are  within  reach  of  the  watei^plane.  The  addition  of  this 
quantity  would  increase  the  computed  ground-water  discharge  from 
the  basin. 

4.  Kelative  to  the  matter  of  underflow  from  the  basin  past  the 
Alabama  Hills,  the  writer  has  given  this  matter  considerable  thought 
at  various  times,  and  cannot  agree  with  Mr.  Smith  as  to  the  probability 
of  there  being  an  appreciable  loss  at  this  point.  For  a  distance  of 
6  miles  from  the  "Point  of  the  Hills"  to  Lone  Pine  Creek  there  are 
no  lateral  streams  breaking  through  the  hills.  The  whole  cross-section 
was  formerly  covered  by  Owens  Lake,  and  any  material  brought  down 
by  Hogback  Creek  would  have  been  deposited  on  the  lake  shore  at  the 
"Point  of  the  Hills",  or,  in  case  of  low  lake  level,  would  have  been 
carried  directly  out  on  the  lake  bed.  There  would  be  no  condition 
favoring  or  even  rendering  possible  the  deposition  in  the  section  of 
any  but  the  finest  materials,  even  on  the  side  adjoining  the  steep  slope 
of  the  Alabama  Hills.  Further,  there  is  the  elevated  water-plane 
of  the  Lone  Pine  delta  opposing  such  underflow,  and  the  absence 
of  any  evaporating  area  which  would  naturally  result  from  the  back- 
water effect.  Finally,  there  is  the  fact  that  the  valley  floor  of  the 
Independence  Basin  above  the  Alabama  Hills  is  an  old  lake  bed 
beneath  which  fine  sands  and  clays  predominate,  that  the  porous 
gravels  of  the  outwash  slope  surround  this  relatively  non-porous  core, 
that  ground-water  percolating  laterally  through  the  gravels  meets  a 
barrier  at  the  old  lake  shore  and  is  compelled  to  seek  an  outlet  locally 
by  spring  flow  and  evaporation,  and  that,  therefore,  the  conditions 
necessary  for  an  active  underflow  down  stream  are  entirely  lacking 
throughout  the  whole  of  the  valley  floor. 

The  discussion  of  probable  annual  variations  in  safe  yield  is  not 
of  such  great  importance  for  the  Independence  Basin  as  in  other  basins. 
This  is  due  to  two  reasons,  the  immense  storage  capacity  of  the  satu- 
rated gravels  and  the  non-porous  core  or  heart  of  the  valley.  The 
former  is  relatively  very  large  with  respect  to  any  judiciously  developed 
draft,  and  the  latter  holds  up  the  water-plane  and  prevents  the  escape 


250         DISCUSSION :  yield  of  underground  reservoirs 

Mr.  of  water  from  the  basin  by  underflow.  Thus,  the  fluctuation  of  the 
^^'  water-plane  within  a  reasonable  distance  of  the  old  lake  shore  would 
not  be  great,  even  in  periods  of  extended  drought.  The  effect  of 
variations  in  ground-water  supply  in  the  Independence  Basin  would 
appear  more  as  variation  in  spring  flow  and  evaporation  loss  than 
as  fluctuation  in  the  water-plane. 

Mr.  Meinzer's  long  and  intimate  experience  and  scientifi.c  study 
of  the  problems  involved  in  this  paper  make  him  one  of  the  best 
qualified  men  in  America  to  discuss  it,  and  his  contribution  has  added 
greatly  to  its  value.  The  writer,  however,  feels  that  in  general  his 
discussion  is  from  the  point  of  view  of  the  pure  scientist  who  strives 
for  absolute  accuracy,  rather  than  from  that  of  the  applied  scientist 
or  engineer  whose  aim  is  relative  accuracy.  There  were  involved  in 
the  solution  of  this  particular  problem  not  only  questions  of  obtaining 
a  proper  internal  balance  in  relative  accuracy,  but  also  that  of  giving 
the  problem  its  proper  place  in  the  larger  one  of  determining  the  safe 
yield  from  all  sources  available  for  a  large  municipal  water-supply 
project.  The  quantity  of  ground-water  available  for  development 
from  the  Independence  Basin  is  about  one-fifth  of  that  available 
from  all  sources.  The  writer  believes  the  results  obtained,  as  set  forth 
in  this  paper,  are  well  within  the  limits  of  reasonable  accuracy  for 
the  purpose  desired.  Considered  in  this  light,  he  does  not  agree  with 
Mr.  Meinzer  that  the  assumptions  are  "subject  to  large  errors." 

Considering  Mr.  Meinzer's  discussion  in  detail,  the  writer  is  in- 
debted to  him  for  drawing  attention  to  the  erroneous  inclusion  with 
ground-water  discharge  of  18  sec-ft.  of  irrigation  water  dissipated 
by  evaporation  and  transpiration.  As  has  been  pointed  out  by  both 
Messrs.  Smith  and  Meinzer,  however,  there  is  an  appreciable  loss  from 
rank  desert  vegetation  bordering  the  shallow  ground-water  area..  The 
inclusion  of  this  with  ground-water  losses  would  increase  the  latter, 
and,  therefore,  the  corrections  in  the  final  result  would  tend  to  offset 
one  another. 

Mr.  Meinzer  states  that  observations  covering  1,  2,  or  3  years  do 
not  give  average  evaporation  conditions,  comparing  them  with  pre- 
cipitation and  stream-gauging  data  in  this  respect.  The  writer  does 
not  believe  that  this  statement  would  have  been  made  if  evaporation 
records  covering  several  years  had  been  examined.  The  range  of 
annual  variation  in  evaporation  is  usually  less  than  4%,  whereas  pre- 
cipitation and  stream  flow  may  have  extreme  variations  of  more  than 
100  per  cent. 

Mr.  Meinzer  suggests  that,  in  order  to  apply  the  results  of  the 
Owens  Valley  evaporation  experiments  to  other  valleys,  it  would  be 
necessary  to  have  a  large  number  of  observation  wells  and  keep  them 
under  observation  for  several  years.  The  writer's  experience  in  other 
valleys  during  the  past  3  years  has  been  that  water-plane  fluctuations 


discussion:  yield  of  undergrouxd  reservoiks  251 

in   evaporation   areas   follow   the   same   annual  periodic   law   observed,  Mr. 
and  have  about  the  same  range  as  observed  in  Owens  Valley.     Hence 
the  observation   of  a  few  judiciously  chosen  wells  at  a  critical   date, 
preferably  late  in  September,  should  give  dependable  results. 

The  writer  agrees  heartily'  with  Mr.  Meinzer  that  further  investi- 
gations of  soil  evaporation  and  transpiration  under  various  conditions 
should  be  made.  In  connection  with  the  rate  of  evaporation  from  bare 
alkaline  lake  beds  or  "playas",  certain  experiments  recently  carried 
on  under  the  writer's  direction  tend  to  confirm  Mr.  Meinzer's  observa- 
tions. The  evaporation  from  two  pans  of  water  under  exactly  similar 
conditions  was  observed,  one  pan  containing  distilled  water  and  the 
other  a  sample  of  highly  alkaline  lake  water.  The  rate  of  evaporation 
from  the  denser  water  was  less  than  that  from  the  fresh  water,  and 
rapidly  decreased  to  a  very  small  value  as  the  salts  began  crystallizing 
out,  regardless  of  the  fact  that  no  permanent  crust  was  allowed  to  form. 

The  writer  is  very  glad  that  Mr.  Horton  has  emphasized  the  fact 
that  in  the  development  of  hydrographic  projects  the  most  important 
feature,  that  is,  water  supply,  is  seldom  given  the  adequate  investiga- 
tion that  it  requires.  The  writer  has  in  mind  several  irrigation 
projects  which  are  either  partial  or  complete  failures  solely  because 
insufficient  stud.y  was  made  of  the  available  water  supply. 

Although  familiar  with  the  work  of  the  German  experimenters 
on  soil  evaporation  and  transpiration  which  Mr.  Horton  cites,  the 
writer  found  that  the  climatic  and  soil  conditions  under  which  their 
experiments  were  performed  were  quite  different  from  those  in  Owens 
Valley,  and  that  the  experimental  equipment  did  not  reproduce  as 
closely  as  seemed  desirable  the  natural  conditions.  Hence,  he  found 
it  impractical  to  follow  their  precedents  as  closely  as  would  seem 
possible  at  first  glance. 

In  comment  on  Mr.  Horton's  suggestion  that  tables  of  rainfall 
and  run-off  would  have  added  to  the  value  of  the  paper,  the  writer 
wishes  to  draw  attention  to  Article  VI,  Section  11,  of  the  Constitution 
of  the  Society,  which  contains  the  statement  that  "papers  offered  for 
presentation  ^*  ^'  '■'  containing  matter  readily  found  elsewhere 
"■     *     *     shall  be  rejected." 

The  writer  takes  exception  to  ]\Ir.  Horton's  statement  that  there 
is  no  increment  of  flow  during  the  frozen  season  to  the  mountain 
streams  tributary  to  Owens  Valley.  Although  it  is  true  that  the  sur- 
face of  the  snow  is  frozen,  yet  on  the  under  side,  in  contact  with  the 
soil,  containing  more  or  less  stored  heat,  there  is  a  slow  but  continual 
melting  which  contributes  a  permanent  supply  to  stream  flow  all 
winter.  This  is  proved  by  the  observed  fact  that  if  freezing  weather 
occurs  before  the  first  snowfall,  the  streams  show  material  reduction 
in  flow,  but  that,  soon  after  the  mountain  slopes  are  snow-covered, 
there  is  a  return  to  normal  Avinter  flow. 


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